EG&G 113 Service manual

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MOEL 113
LOW- NOISE
PREAMPLIFIER
SEE SAFETY NOTICE
PRECEDNG SECTION I
BEFORE OPERATING INSTRUMENT
NG AND SERVICE MANUAL
/
MODEL 113
LOW -NOISE
PREAMPLIFIER
S EE SAFETY NOTICE
PRECEDNG SECTION I
BEFORE OPERATING INSTRUMENT
HF RO LL ·OFF
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11 3
PRE · AMP
OPERATING AND SE RVICE MANUAL

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MODEL 113
LOW-NOISE
PREAMPLIFIER
OPERATING AND INSTRUCTION MANUAL
(;;n~EGc..G PRINCETON APPLIED RESEARCH
Copyright ©1983 EG&G PRINCETON APPLIED RESEARCH Printed In U.S.A.

SHOULD YOUR EQUIPMENT REQUIRE SERVICE WARRANTY
A. Contact the factory (609/452-2111) or your local factory EG&G PRINCETON APPLIED RESEARCH warrants each in-
representative to discuss the problem. In many cases it strument of its manufacture to be free from defects in material Q
will be possible to expedite servicing by localizing the and workmanship. Obligations under this Warranty shall be
problem to aparticular plug-in circuit board. limited to replacing, repairing or giving credit for the purchase
price, at our option, of any instrument returned, freight
B. If it is necessary to send any equipment back to the fac- prepaid, to our factory within ONE year of delivery to the
tory, we need the following information. original purchaser, provided prior authorization for such return
has been given by our authorized representative.
(1) Model number and serial number. This Warranty shall not apply to any instrument which our in-
(2) Your name (instrument user). spection shall disclose to our satisfaction, has become defec-
tive or unworkable due to abuse, mishandling, misuse, acci-
(3) Your address. dent, alteration, negligence, improper installation or other
causes beyond our control. Instruments manufactured by
(4) Address to which instrument should be returned. others, and included In or supplied with our equipment, are not
covered by this Warranty but carry the original manufacturer’s
(5) Your telephone number and extension. warranty which is extended to our customers and may be more
restrictive. Certain subassemblies, accessories or com-
(6) Symptoms (in detail, including control settings). ponents may be specifically excluded from this Warranty, in
which case such exclusions are listed in the Instruction
(7) Your purchase order numberfor repair charges (does Manual supplied with each instrument.
not apply to repairs in warranty). We reserve the right to make changes in design at any time
(8) Shipping instructions (if you wish to authorize ship- without incurring anyobligation to install same on units
ment by any method other than normal surface previously purchased. 1
transportation). THERE ARE NO WARRANTIES WHICH EXTEND BEYOND THE
C. U.S. CUSTOMERS—Ship the equipment being returned DESCRIPTION HEREIN. THIS WARRANTY IS IN LIEU OF, AND
to: EXCLUDES ANY AND ALL OTHER WARRANTIES OR REPRE-
SENTATIONS, EXPRESSED, IMPLIED OR STATUTORY, IN-
EG&G PRINCETON APPLIED RESEARCH CLUDING MERCHANTABILITY AND FITNESS, AS WELL AS
7Roszel Road ANY AND ALL OTHER OBLIGATIONS OR LIABILITIES OF
(Off Alexander Road, East of Route 1) EG&G PRINCETON APPLIED RESEARCH, INC_UDING, BUT
Princeton, New Jersey NOT LIMITED TO, SPECIAL OR CONSEQUENTIAL DAMAGES.
NO PERSON, FIRM OR CORPORATION IS AUTHORIZED TO
D. CUSTOMERS OUTSIDE OF U.S.A.—To avoid delay in ASSUME FOR EG&G PRINCETON APPLIED RESEARCH ANY D
customs clearance of equipment being returned, please ADDITIONAL OBLIGATION OR LIABILITY NO“ EXPRESSLY
contact the factory or the nearest factory distributor for PROVIDED FOR HEREIN EXCEPT IN WRITING DULY EXE-
complete shipping information. CUTED BY AN OFFICER OF EG&G PRINCETON APPLIED
RESEARCH.
E. Address correspondence to:
EG&G PRINCETON APPLIED RESEARCH
P. O. Box 2565
Princeton, NJ 08540
Phone: [phone]
TELEX: 84 3409
3
SHOULD YOUR EQUIPMENT REQUIRE SERVICE
A. Contact the factory (609/452·2111) or your local factory
representative
to discuss the problem. In many cases it
will
be possible to expedite servicing by localizing the
problem to a particular plug·in
circuit board.
B. If it is necessary to send any equipment back to the fac·
tory, we need the
following information.
(1) Model number and serial number.
(2) Your name (instrument user).
(3) Your address.
(4) Address to which instrument should be returned.
(5) Your telephone number and extension.
(6) Symptoms (in detail, including control settings).
(7) Your purchase order number for repair charges (does
not apply to repairs in warranty).
(8) Shipping instructions (if you wish to authorize ship·
ment
by any method other than normal surface
transportation).
C. U.S. CUSTOMERS-Ship the equipment being returned
to:
EG&G PRINCETON APPLIED RESEARCH
7 Roszel Road
(Off Alexander Road, East of Route
1)
Princeton, New Jersey
D. CUSTOMERS OUTSIDE OF U.SA- To avoid delay in
customs clearance of equipment being returned, please
contact the factory or the nearest factory distributor for
complete shipping information.
E. Address correspondence to:
EG&G PRINCETON APPLIED RESEARCH
P. O. Box 2565
Princeton, NJ 08540
Phone: 609/452·2111
TELEX: 84 3409
WARRANTY
EG&G PRINCETON APPLIED RESEARCH warrants each in-
strument
of its manufacture to be free from defects in material ~
and workmanship. Obligations under this Warranty shall be
limited to replacing, repairing or giving credit for the purchase
price, at our option, of any instrument returned, freight
prepaid,
to olJr factory within ONE year of delivery to the
original purchaser, provided prior authorization
for such return
has been given by our authorized representative.
This Warranty shall not apply
to any instrument which our in·
spection shall disclose to our satisfaction, has become defec·
tive
or unworkable due to abuse, mishandling, misuse, acci·
dent, alteration, negligence, improper installation
or other
causes beyond our control. Instruments manufactured by
others, and included in
or supplied with ourequipment, are not
covered by
this Warranty but carry the original manufacturer's
warranty which is extended
to our customers and may be more
restrictive. Certain subassemblies, accessories
or com-
ponents may
be specifically excluded from this Warranty, in
which case such exclusions are listed in the
Instruction
Manual supplied with each instrument.
We reserve the right to make changes in design at any time
without incurring any obligation to install same on units
previously purchased.
THERE
ARE NO WARRANTIES WHICH EXTEND BEYOND THE
DESCRIPTION HEREIN. THIS WARRANTY IS
IN LIEU OF, AND
EXCLUDES ANY AND
All OTHER WARRANTIES OR REPRE·
SENTATIONS, EXPRESSED, IMPLIED
OR STATUTORY, IN·
ClUDING MERCHANTABILITY AND FITNESS, AS WELL AS
ANY AND ALL OTHER OBLIGATIONS OR LIABILITIES OF
EG&G PRINCETON APPLIED RESEARCH, INCLUDING, BUT
NOT LIMITED TO, SPECIAL OR CONSEQUENTIAL DAMAGES.
NO PERSON, FIRM OR CORPORATION IS AUTHORIZED TO
ASSUME
FOR EG&G PRINCETON APPLIED RESEARCH ANY ~
ADDITIONAL OBLIGATION OR LIABILITY NOT EXPRESSLY
PROVIDED
FOR HEREIN EXCEPT IN WRITING DULY EXE-
CUTED BY AN OFFICER OF EG&G PRINCETON APPLIED
RESEARCH.

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TABLE OF CONTENTS
r Section
Page
CHARACTERISTICS 1-1
1:1
Introduction
1-1
1.2 Specifications
1-1
II INITIAL CHECKS 11-1
2.1
Introduction
11·1
2.2 Equipment Needed 11·1
2.3 Procedure
11-1
III
OPERATING INSTRUCTIONS
111-1
3.1 I
ntrodu ction 111-1
3.2 Noise and Source Resistance 111-1
3.3 Grounding 111-2
3.4 Signal Voltage and Gain
3.5 Dc Zero Adjustment
111-2
3.6 Overload Fast Recovery 111-3
3.7 Low-Pass/High·Pass Filters 111-3
3.8 Single-Ended/Differential Operation
111-3
3.9 Common-Mode Rejection
and Dc Zero Adjustments
111-4
3.10 Maximum
Input Signal Consistent with Linear Operation 111-4
3.11 Battery Operation, Test, and Charging 111·5
3.12 Rack Mounting 111-5
3.13 Using a Signal
Input Transformer
111·6
3.14 Use of the Model 113 in Bio-Medical Applications
111-12
,...,..
IV . CIRCUIT DESCRIPTION
IV-l
4.'
Block Diagram Discussion
IV-l
4.1A Input Coupling Circuit IV-1
4.1B Ground·Loop Suppression IV-1
4.1C Gain Determination IV-1
4.10 Rolloff Filter Circuit
IV-'
4.1 E Overload Fast-Recovery Circuit
IV-2
4.1 F Power Supply
IV-2
4.2 Circuit Descriptions IV-2
4.2A
Differential Preamplifier (A 1)
IV-2
4.2B
Output Amplifier (A2)
IV-3
4.2C Power Supply
Circuit
IV-3
4.2D Battery Test
Circuit
IV-3
V
ALIGNMENT PROCEDURE
V-l
5.1
Introduction
V-l
5.2 Preliminary
V·l
5.3 Equipment Needed V·1
5.4
A2 FET Gate Source Zero Adj.
V·1
5.5 Common-Mode Rejection Adj. V-l
5.6 Gain Calibration
V-'
5.7
Low Frequency Rolloff Compensation V-2
5.8 High Frequency
Rolloff Compensation V·2
5.9 Battery Test Calibrate V-2
VI
TROUB LESHOOTI NG
VI-l
6.1
Introduction
VI-l
6.2 Procedure
VI·'
,..
6.3 Printed Circuit Soldering
VI·l
\,,~
VII
SCHEMATICS V
11-'

Number 'Page
cb<.'o<5o§iov<':-ii:-<Lo|i>L~
09>
-'0
-'1
-'3
I‘I‘I‘I‘I‘
LOOO\lO>U'lJ>~
-20
V-1
VI-1
-'2A
-'28
FIGURES
ypical Recovery Time vs Low Frequency Rolloff . . .'
_P Filter Normalized Amplitude Transfer Curve ...
HP Filter Normalized Amplitude Transfer Curve ...
_P/HP Filter Normalized Phase Transfer Curve . . .
Typical Common Mode Rejection Characteristics . . . . . . . . . . .
Vlaximum Differential Input to Model 113 . . . . . . . . . . . .. . .
Vlodifying the AM-1 Transformer for Use with the Model 113 Preamplifier . . .
Frequency Response of Typical Model AM-1 Transformer .. . . . . . . .
Noise Figure Contours for Typical Model AM-1 Transformer . . . . . . .
Schematic of Model AM-1 Transformer (Unmodified) . . .'.
Photographs of Model AM-1 Transformer . . ... . . ..
Frequency Response of Typical Model AM-2 Transformer . . ..
Noise Figure Contours for Typical Model AM-2 Transformer . . .
Model AM-2 Schematic, Turns Ratio 1:100 . . . . . ... .
Phot0ofModelAM-2 ................ .
Frequency Response of Typical Model 190 Transformer ..
Noise Figure Contours for Typical Model 190-113 System . . .
Ground-Loop Current Path ..IV
Solder Removal byWicking ..VI1
..Vl1
Typical Noise Figure Contours for the Model 113 ..ll 1,D
ll-3
II4
II4
ll-4
II4
III5
ll-6
Ill-6
lll6
III7
Ill-7
llI8
lll8
Ill-8
lll9
lll9
lll9
Model190Schematic ............... ..lll-10
Photograph of Model 190 Transformer .. . .Ill-10
B-H Curve &Waveform . . . .. . ...Ill-10
Degaussing Waveforms .. . ..Ill-11
Number
1-1
1-2
1-3
1-4
1-5
1-6
1-7
1-8
1-9A
1-98
1-10
1-11
1-12A
1-128
1-13
1-14
1-15
1-16
11-17
11-18
11-19
11-20
V-l
VI-l
FIGURES
Typical Noise Figure Contours for the Model 113
Typical Recovery
Time vs Low Frequency Rolloff
LP Filter Normalized Amplitude Transfer Curve
HP Filter Normalized Amplitude Transfer Curve
LP/HP
Filter Normalized Phase Transfer Curve
Typical Common Mode Rejection Characteristics
Maximum Differential
Input to Model 113
Modifying the AM-l Transformer for Use with the Model 113 Preamplifier
Frequency Response
of Typical Model AM-l Transformer .
Noise Figure Contours
for Typical Model AM-l Transformer
Schematic
of Model AM-l Transformer (Unmodified)
Photographs of Model AM-l Transformer ....... .
Frequency Response
of Typical Model AM-2 Transformer .
Noise Figure Contours
for Typical Model AM-2 Transformer
Model
AM-2 Schematic, Turns Ratio 1: 100 .....
Photo of Model AM-2 . . . . . . . . . . . . . . .
Frequency Response
of Typical Model 190 Transformer
Noise Figure Contours
for Typical Model 190-113 System
Model 190 Schematic . . . . . . .
Photograph
of Model 190 Transformer
B-H Curve & Waveform
Degaussing Waveforms . .
Ground-Loop Current Path
Solder Removal
by Wicking
• Page
111-'
~.
1-3
1-4
1-4
1-4
I 1-4
I 1-5
I 1-6
I 1-6
I 1-6
111-7
111·7
111-8
111-8
111-8
111-9
111-9
111-9
111-10
111-10
111-10
111-11
IV-l
VI-l
. VI-l

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EIOI.I.ON M.EI=IVS
SAFETY NOTICE
(Read Before Operating Instrument)
A. INTRODUCTION
The Model 113 to which this instruction manual
applies has been supplied in a safe condition.
This manual contains some information and warn-
ings
that have to be followed by the user to ensure
safe operation and to retain the instrument in a
safe condition.
The described apparatus has been designed for
indoor use.
B. INSPECTION
Newly received apparatus should be inspected for
shipping damage. If any is noted,
notify EG&G
PARC and file a claim with the carrier. Be sure to
save the shipping container for inspection by the
carrier.
WARNING!
THE PROTECTIVE GROUNDING COULD
BE
RENDERED INEFFECTIVE IN DAMAGED Ap·
PARATUS. DAMAGED APPARATUS SHOULD
NOT
BE OPERATED UNTIL ITS SAFETY HAS
BEEN VERIFIED
BY QUALIFIED SERVICE PER-
SONNEL. DAMAGED APPARATUS WAITING FOR
SAFETY VERIFICATION SHOULD BE TAGGED TO
INDICATE TO A POTENTIAL USER THAT IT MAY
BE UNSAFE AND THAT IT SHOULD NOT BE
OPERATED.
C. SAFETY MECHANISM
As defined in IEC Publication 348 (Safety Require-
ments
for Electronic Measuring Apparatus), the
Model 113, when operated from the ac line, is
Class I apparatus, that is, apparatus that depends
on connection
to a protective conductor to earth
ground for equipment and operator safety. Before
any
other connection is made to the apparatus,
the protective connection is made via the earth
ground prong
of the power cord plug. The power
cord plug shall
only be inserted in a socket outlet
provided
with the required earth ground contact.
The protective action must not
be negated by the
use
of an extension cord without a protective con-
ductor, by use
of an "adapter" that doesn't main-
tain earth ground continuity, or by any other
means.
WARNING!
ANY INTERRUPTION OF THE PROTECTIVE CON-
DUCTOR INSIDE
OR OUTSIDE THE APPRATUS
OR DISCONNECTION OF THE PROTECTIVE
EARTH TERMINAL MAY MAKE THE APPARATUS
DANGEROUS. INTENTIONAL INTERRUPTION
IS
PROHIBITED.
The power cord plug provided is
of the type illus-
trated in Figure
1. If the provided plug is not com-
patible with the available power sockets, the plug
or power cord should be replaced with an approv-
ed type of compatible design.
WARNING!
IF
IT IS NECESSARY TO REPLACE THE POWER
CORD
OR TH E POWER CORD PLUG, TH ERE·
PLACEMENT CORD OR PLUG MUST HAVE THE
SAME POLARITY
AS THE ORIGINAL. OTHER-
WISE A SAFETY HAZARD FROM ELECTRICAL
SHOCK, WHICH COULD RESULT
IN INJURY OR
DEATH, MIGHT RESULT.
When operated from
its internal battery with the
line cord disconnected, the Model
113 could be
considered Class
III apparatus, that is, apparatus
in which protection against electric shock relies
on supply at safety extra-low voltage (SELV) and in
which voltages higher than those
of SELV are not
generated. When operated battery powered and
with the line cord disconnected, the voltage levels
inside the Model
113 will nofexceed ± 12 V. This
does not take into account the
possibility of
higher voltages being applied via the signal input
or
output cables.
D. POWER VOLTAGE SELECTION
Before plugging in the power cord, make sure that
the instrument is set for operation from the
voltage
of the ac power supply.
CAUTION!
THE APPRATUS DESCRIBED
IN THIS MANUAL
MAY
BE DAMAGED IF IT IS SET FOR OPERATION
FROM
110 V AC AND TURNEDON WITH 220 V AC
APPLIED TO THE POWER INPUT CONNECTOR.
The line voltage is selected by means
of a rear·
panel switch.
FOR SAFETY, UNPLUG THE
E
L
L= LINE OR ACTIVE CONDUCTOR (ALSO CALLED "LIVE" OR "HOT")
N =NEUTRAL OR IDENTIFIED CONDUCTOR
E =
EARTH OR SAFETY GROUND
Figure 1. POWER CORD PLUG WITH POLARITY INDICATIONS

POWER CORD WHEN CHANGING THE LINE with normal heart functioning. However, recent
VOLTAGE SETTING. Depend'ng on the switch research has shown that dangerexists at far lower
position, either “115” or “230” (both are printed on current levels than was previously suspected. As
the switch) will be visible to the operator. For aconsequence of this increased awareness, and
operation from aline voltage of nominally 115 Vafter acareful analysis of the Model 113 design,
ac, the switch should be set so that “115” shows. EG&G Princeton Applied Research Corporation
For operation from aline voltage of nominally feelsthat it cannot recommend the Model 113for
230 Vac, “23O” should show. use in applications involving human subjects or
patients. In certain situations involving specific
conditions of grounding, internal component
E. LINE FUSE failure, or excessive common-mode input, the
The Model 113 line fuse is located inside the in- high input impedance of the Model 113 could fail
strument. To check or replace the fuse, it is first and potentially dangerous currents could flow
necessary to remove the top cover and also the through the subject.
shield mounted on the inside of the rear panel.
The fuse should be aslow-blow type rated at However, the reader should not get the impres-
either 1/16 A(115 VOperation) or 1/32 A(230 Vsion that the Model 113 is in any wayadangerous
operation). The voltage rating should be 125 Vor instrument to use in ordinary applications. Those
higher in the Case 01 115 VOperation and 250 Vor characteristics that necessitate the advisory
hiélherththe eeee Qt 230V0DeFeti0i1-9h|YeBU$$ against the instrument’s use in bio-medical ap-
MDL OF equh/eteht thee Sheuld be USed- plications with humans are common to most other
preamplifiers as well. In fact, with its low internal
wA|=tNiN(;i supply voltages, capability for internal battery
TO AVOID THE POSSIBILITY o|= ASAFETY HAZ- power with epinpieie independence of the ep line.
ARD FRQM E|_ECTR|CA|_ SHQCK wi-ii(3i-i (3QUi_|3 and extremely high input impedance under normal
REsui_T |N INJURY OR DEATH, |)|$(;()Ni\|EcT operating conditions, the Model 113 is probably
THE PQWER CORD BEFQRE REM()V|NG QR |i\|- one of the safest preamplifiers available for
$"i'Ai_i_|N(3 AFU$E_ i3E(;Ati$E QF Ti-ii; PQTEN- general use. For all practical purposes, it can be
T|A|_ HAZARD, Ti-ii; FUSE Si-|()U|_[) BE CHECKED considered to be completely harmless. The maxi-
AND/OR CHANGED BY AQUALIFIED SERVICE mum internei Supply vpitepee eppiied tp the em-
"|'E(3i-i|\ii(3iAN ()Ni_Y_ plifiers are only i12 V. Even these low voltages
can only appear at the input under very specific
Aprooeoure for geinino eooeee to the fuse operating conditions, and then generallyforonlya
follows. few milliseconds. Aperson inadvertently touching
the input under these conditions would, in
(1) Remove the top oover_ it is eeoureo by egeneral, not even be aware that there was any
single screw on the bottom surface ofthetop- Vettege there at ett ehd hY he etfeteh Qt the im-
oover “tip” et the reer of the inetrument_ with agination could the operator of the instrument be
the screw removed, the cover simply slides ie9eTded ee hethg ih ehY dehgeh
back to where it can be freed from the instru-
ment_ The preamplifier can be used in biological appli-
cations involving animal subjects. However, if the
(2) Remove the shield attached to the inside of eppiieeiipn ie pne in whieh ekin reeieienee is
the rear panel. This shield is secured by adreetivredueed prbvpeeeed.tne pperetprie advis-
einoie eorew at its oenter_ with the ehieio ed to observe the following recommendations if
removeo, the iuee hoioer, iooeteo oireotiy unnecessary risk to the experimental animal isto
above the Line Voltage Selector switch, he evetdeti
becomes accessible. 1(1) Turn the amplifier power on BEFORE making
(3) After oheokino eno, it eppropriete, ohenging any connections to the experimental animal.
the fuse, remount the shield and top cover
before plugging in the line cord and operating (2) set the thput Ceuhtthg ewttehee 01 the Medet
the inetrument_ 113 to GND before making any connections to
the experimental animal. Do not transfer from
the GND settings until after the connections
are completed.
F. USE OF THE MODEL 113 IN 1
BIO-MEDICAL APPLICATIONS (3) Do not turn the power switch on or off while
In the past few years, safety in bio-medical ap- the instrument is connected to the experi-
plications has been amatter of growing concern mental animal.
to both the users and suppliers of electronics
equipment. It has long been known that electrical It may prove helpful to consider the reason for
currents passing through the heart can interfere these precautions. By understanding them, the
3
—_---up
POWER CORD WHEN CHANGING THE LINE
VOLTAGE SETTING. Depending on the switch
position, either
"115" or "230" (both are printed on
the switch) will be visible
to the operator. For
operation from a line voltage
of nominally 115 V
ac, the switch should
be set so that "115" shows.
For operation from a line voltage
of nominally
230 V ac, "230" should show.
E. LINE FUSE
The Model 113 line fuse is located inside the in-
strument. To check or replace the fuse, it is first
necessary
to remove the top cover and also the
shield mounted on the inside
of the rear panel.
The fuse should be a slow-blow type rated at
either 1/16 A
(115 V operation) or 1/32 A (230 V
operation). The voltage rating should
be 125 V or
higher in the case
of 115 V operation and 250 V or
higher in the case of 230 Voperation. Only a BUSS
MDL or equivalent fuse should be used.
WARNING!
TO AVOID THE POSSIBILITY OF A SAFETY HAZ-
ARD FROM ELECTRICAL SHOCK WHICH COULD
RESULT
IN INJURY OR DEATH, DISCONNECT
THE POWER CORD BEFORE REMOVING
OR IN-
STALLING A
FUSE. BECAUSE OF THE POTEN-
TIAL HAZARD, THE FUSE SHOULD BE CHECKED
ANDIOR CHANGED
BY A QUALIFIED SERVICE
TECHNICIAN ONLY.
A procedure for gaining access to the fuse
follows.
(1) Remove the top cover. It is secured by a
Single screw on the bottom surface
of the top-
cover
"lip" at the rear of the instrument. With
the screw removed, the cover simply slides
back to where
it can be freed from the instru-
ment.
(2) Remove the shield attached to the inside of
the rear panel. This shield is secured by a
Single screw at its center. With the shield
removed, the fuse holder, located directly
above the Line Voltage Selector switch,
becomes accessible.
(3) After checking and, if appropriate, changing
the fuse, remount the shield and top cover
before plugging in the line cord and operating
the instrument.
F. USE OF THE MODEL 113 IN
BIO·MEDICAL APPLICATIONS
In the past few years, safety in bio-medical ap-
plications has been a matter of growing concern
to both the users and suppliers of electronics
equipment. It has long been known that electrical
currents passing through the heart can interfere
with normal heart functioning. However, recent
research has shown that dangerexists at far lower
current levels than was previously suspected. As
a consequence
of this increased awareness, and
after a careful analysis
of the Model 113 deSign,
EG&G Princeton Applied Research Corporation
feels that it cannot recommend the Model 113 for
use
in applications involving human subjects or
patients.
In certain situations involving specific
conditions
of grounding, internal component
failure, or excessive common-mode input, the
high input impedance
of the Model 113 could fail
and potentially dangerous currents could flow
through the subject.
However, the reader should not get the impres-
sion that the Model 113 is in any way a dangerous
instrument
to use in ordinary applications. Those
characteristics that necessitate the adviSOry
against the instrument's use in bio-medical
ap-
plications with humans are common to mostother
preamplifiers as well.
In fact, with its low internal
supply voltages, capability for internal battery
power with complete independence
of the ac line,
and extremely high input impedance undernormal
operating conditions, the Model 113 is probably
one
of the safest preamplifiers available for
general use. For all practical purposes,
it can be
considered
to be completely harmless. The maxi-
mum internal supply voltages applied
to the am-
plifiers are only ±
12 V. Even these low voltages
can only appear at the input under very specific
operating conditions, and then generally for only a
few milliseconds. A person inadvertently touching
the input under these conditions would, in
general, not even be aware that there was any
voltage there at all and by no stretch
of the im-
agination could the operator
of the instrument be
regarded
as being in any danger.
The preamplifier can be used in biological appli-
cations involving animal subjects. However,
if the
application is one in which skin resistance is
greatly reduced
or bypassed, the operator is advis-
ed to observe the following recommendations if
unnecessary risk to the experimental animal is to
be avoided.
(1) Turn the amplifier power on BEFORE making
any connections
to the experimental animal.
(2) Set the Input Coupling switches of the Model
113 to GND before making any connections to
the experimental animal. Do not transfer from
the GND settings until after the connections
are completed.
(3) Do not turn the power switch on or off while
the instrument is connected
to the experi-
mental animal.
It may prove helpful
to consider the reason for
these precautions. By understanding them, the

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operator may be better able to safely carry out
electrical
monitoring of experimental animals, not
only where the input amplifier is the Model 113,
but where other preamplifiers are used as well.
(1) Turn-On Transients
When the
amplifier is first turned on, all cir-
cuits do not instantly assume their quiescent
operating state. Instead, a
finite time is re-
quired for the common-mode loop amplifier
to set the input stages to their proper operat-
ing point. During
this interval (which varies
from a few
milliseconds to a second or more
depending on the source impedance), the
source-gate
junction of one input transistor
or the other is forward-biased. In this state,
the
transistor does not exhibit a high im-
pedance, but instead appears as a low im-
pedance from the input
of the instrument to
the output of the common-mode amplifier.
(2) Power Transformer
The power transformer in the Model
113 is of
very high quality and is unlikely to fail during
the
life of the instrument. Nevertheless, the
possibility of such a failure, however remote,
must be considered. Should a short develop,
and
if the instrument were being used with in-
complete or improper ground returns (com-
mon in many
buildings and installations), a
dangerous situation would exist.
(3) Internal Component Failure
The input transistors
of the Model 113 are
junction-type field-effect transistors. Al-
though they
exhibit an extremely high input
resistance when properly biased,
their resis-
tance can drop
to a few ohms if their operat-
ing current or bias is
out of the normal operat-
ing range
sufficiently to give a simple forward
biased diode
junction from the gate to either
the source or the drain. There are several
possible internal component failures which,
though unlikely, could bring about
this condi-
tion. Should
it occur, the input of the ampli-
fier would be connected through a low im-
pedance
directly to the instrument's power
supply.
(4) Excessive Common-Mode Input
As stated in the specifications, the common-
mode input
limit of the Model 113 is 1 V rms.
Higher levels
"turn on" low conduction paths
at the input
of the preamplifier to protect the
input circuits, and thereby lowerthe
input im-
pedance.
Again, it should be emphasized that, even though
EG&G Princeton Applied Research Corporation
does not recommend the Model
113 for use with
human subjects, its use in all other applications is
recommended
without reservation.
G. VENTILATION
With a power consumption of only 5 watts when
operated from the ac line, and even less when bat-
tery operated, the Model 113 does not have any
special
ventilation requirements. It can be
operated on a bench or
in a rack (rack mounting
kits can be purchased from the factory), the only
constraint being that the ambient temperature
be
in the range of 15°C to 45 °C.
H. DEFECTS AND ABNORMAL
STRESSES
Whenever it is likely that the protection provided
by the connection
to earth ground has been im-
paired, the apparatus shall be made inoperative
and secured against any unintended operation.
The protection is likely
to be impaired if, for exam-
ple, the apparatus:
(1) Shows visible damage,
(2) Fails to perform the intended measurements,
(3) Has been subjected to prolonged storage
under unfavorable conditions,
(4) Has been subjected to severe transport
stresses.
Such apparatus should not be used until
its safety
has been verified by qualified service personnel.

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INOLLOHS
SECTION I
CHARACTERISTICS
1.1 INTRODUCTION
The Model 113 Low-Noise Preamplifier provides high gain,
low noise amplification of wideband signals from dc to 300
kHz. Adjustable high and
low frequency rolloffs allow the
bandwidth to be reduced. Two inputs, with individual
coupling switches,
allow either differential or single-ended
operation. Calibrated gain
is switch selectable from x10 to
X104 in a 1·2-5 sequence, and an uncalibrated gain vernier
provides
x1 to x2.5 range expansion.
The
unit may be powered either from the ac line or from its
own batteries. The nickel-cadmium batteries recharge
automatically during line operation.
Other features include
an overload fast-recovery switch,
special
circuitry that reduces the effects of ground-loop
currents, front-panel
dc zeroing and common mode rejec-
tion screwdriver controls, and battery test provisions.
The Model 113
is well suited for use as a preamplifier for
other Princeton Applied Research signal processing instru-
ments.
1.2 SPECIFICATIONS
(1) INPUTS
Two channels, each with a three position switch to
provide for ac or dc coupled, single-ended or differen-
tial operation. I
nput connectors are BNC type .
/
\-1
(2) INPUT IMPEDANCE
(a) Ac coupled: through 0.1 J.1F, shunted to ground
with 100 megohms and 15 pF in parallel.
(b) Dc coupled: 1 gigohm, shunted
by 15 pF.
(3) MAXIMUM INPUT WITHOUT DAMAGE
(a) Dc coupled: Common-Mode, ±10 V; Differen-
tial, ±7.5 V.
(b) Ac coupled: coupling capacitors can withstand
200 V. Transients which pass through coupling
capacitors cannot exceed dc coupled operation
limits.
(4) MAXIMUM INPUT SIGNAL CONSISTENT WITH
LINEAR OPERATION (see Subsection 3.10)
(a) Common mode: 1 V rms.
(b)
Differential mode (gains of 10 to 100): ±500
mY.
(c) Differential mode (gains of 200 through 10 k):
±50 mY.

(5) COMMON MODE REJECTION (11) OUTPUT VOLTAGE
FREQUENCY FOR GAIN >200 FOR GAIN <200 10 volts pk-pk ahead of 600 ohms.
dc to 100 Hz 120 dB (min) 100 dB (min) (12) OUTPUT IMPEDANCE
1kHz 100 dB 80 dB
10 kHz 80 dB 60 dB 600 ohms.
100 kHz 60 dB 40 dB (13) OVERLOAD RECOVERY
(6) GA|N Resets immediately with spring-loaded front-panel
toggle. See Figure Ill-2 for characteristic recovery
x10 to x104 calibrated gain settings. Accuracy of data-
calibrated gains is i2% when gain vernier is in the (14) P()\/\/ER REQU|RE|\/|E|\|TS
calibrate position. Gain vernier provides uncalibrated
gain F8099 eXl3>an$i0n 01 LID ‘£0 X2-5(fT\ilmUm)- (a) Rechargeable nickel-cadmium batteries provide
approximately 30 hours operation bet\/veen
(7) FREQUENCY RESPONSE charges. Afront-panel, three-position, spring-
loaded toggle switch and test lamp permit test of
Rolloff frequencies are switch selectable. Front panel each of the -[W0 in-[ema| bat-(erie5_
switch markings indicate 3dB point of 6dB/octave
rolloff curve. Rolloffs are selectable as follows: (b) AC |ine Operation; 195-125 \/ ac or 210-259 \/
ac, 50-60 Hz, 5watts. Internal batteries will
(8) I-OW FFBQUBHCVI d¢ P050100 and 0-03 HZ ‘E0 Irecharge automatically while unit is connected to
kHz positions in 1-3-10 sequence. ac power line_
(b) High Frequency: 3Hz to 300 kHz in 1-3-10 (15) DIMENSIONS
sequence. 8.6" Wx4.1" Hx11.3" D(21.8 cm x10.4 cm x28.7
(8) NOISE cm).
At 10 Hz with a2megohm source impedance, noise (16) WEIGHT
figure is 0.3 dB maximum. At 1kHz with a1megohm
source impedance, noise figure is 0.2 dB maximum. 4pounds (1.8 kg).
See Section Ill for further discussion and noise figure
contours. (17) ACCESSORIES
(9) DC DRIFT If the source impedance is less than 100 ohms, best
low-noise performance will be obtained if aModel
(a) Referred to input (dc coupling): maximum 10 AM-1, AM-2, or 190 input transformer is used. Both
‘I-IV/QC Or I688 than 10 /1V/24 hours at constant the AM-1 and the AM-2 have 1:100 turns ratios. The
ambient temperature. Afront panel screwdriver AM-1 has a3dB bandwidth Qf fr()m 1kHz to 10 kHz
control provides for dc Zeroing. at 10 ohms source impedance, and the AM-2 has a
bandwidth of from 1kHz to 150 kHz with a1ohm
(bl Referred to Output: less than 1mv/CC’ or less source. The Model 190 has a1:10:100 turns ratio. The
than 1mv/24 hours at Constant ambmnt tern‘ three dB bandwidth is from 0.25 Hz to 500 Hz with a
peratum 1ohm source. See Section lll for further details
regarding these transformers.
(10) DISTORTION Flanges are available for mounting on asingle unit or
two units side by side in a19" relay rack. See
Typicaldistortion is less than 0.01%. Subsection III-12 for the part numbers of these
flanges.
I-2
(5) COMMON MODE REJECTION
FREQUENCY
dc to 100 Hz
1 kHz
10
kHz
100 kHz
(6)
GAIN
FOR GAIN> 200
120 dB (min)
100
dB
BOdB
60 dB
FOR
GAIN <200
100 dB (min)
BO dB
60 dB
40 dB
x10 to X104 calibrated gain settings. Accuracy of
calibrated gains is ±2% when gain vernier is in the
calibrate position. Gain vernier provides uncalibrated
gain range expansion of up to x2.5 (minimum).
(7) FREQUENCY RESPONSE
Rolloff frequencies are switch selectable. Front panel
switch markings indicate
~ dB point of 6 dB/octave
roll off curve. Rolloffs are selectable as follows:
(a) Low Frequency: dc position and 0.03 Hz to
kHz positions in 1-3-10 sequence.
(b) High Frequency: 3 Hz
to 300 kHz in 1-3-10
sequence.
(B) NOISE
At 10 Hz with a 2 megohm source impedance, noise
figure
is 0_3 dB maximum_ At 1 kHz with a 1 megohm
source impedance, noise figure
is 0.2 dB maximum_
See Section III for further discussion and noise figure
contours.
(9) DC
DRIFT
(a) Referred to input (dc coupling): maximum 10
"IlV/C or less than 10 IlV/24 hours at constant
ambient temperature. A
front panel screwdriver
control provides for dc zeroing.
(b) Referred
to output: less than 1 mV/C, or less
than 1 mV/24 hours at constant ambient tem-
perature.
(10)
DISTORTION
Typical distortion is less than 0.01%.
1-2
(11) OUTPUT VOLTAGE
10 volts pk-pk ahead of 600 ohms.
(12)
OUTPUT IMPEDANCE
600 ohms.
(13)
OVERLOAD RECOVERY
Resets immediately with spring-loaded front-panel
toggle.
See Figure 111-2 for characteristic recovery
data.
(14) POWER
REQUIREMENTS
(a) Rechargeable nickel-cadmium batteries provide
approximately 30 hours operation between
charges. A front-panel, three-position, spring-
loaded toggle switch
and test lamp permit test of
each of the two internal batteries.
(b) Ac line operation: 105-125 V ac or 210-250 V
ac, 50-60 Hz, 5 watts. Internal batteries will
recharge automatically while unit is connected to
ac power line.
(15) DIMENSIONS
B.6" W x 4.1" H x 11.3" D (21.B cm x 10.4 cm x 2B.7
cm).
(16)
WEIGHT
4 pounds (1.B kg).
(17) ACCESSORIES
If the source impedance is less than 100 ohms, best
low-noise performance
will be obtained if a Model
AM-1, AM-2,
or 190 input transformer is used. Both
the AM-1 and the AM-2
have 1: 100 turns ratios. The
AM-1
has a 3 dB bandwidth of from 1 kHz to 10 kHz
at 10 ohms source impedance,
and the AM-2 has a
bandwidth
of from 1 kHz to 150 kHz with a 1 ohm
source. The Model 190
has a 1:10: 1 00 turns ratio. The
three dB bandwidth
is from 0.25 Hz to 500 Hz with a
1 ohm source.
See Section III for further details
regarding these transformers.
Flanges
are available for mounting on a single unit or
two units side by side in a 19" relay rack. See
Subsection 111-12 for the part numbers of these
flanges.
J

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ll NOLLOHS
SECTION II
INITIAL CHECKS
2.1 INTRODUCTION
The following procedure is provided to facilitate initial
performance checking of the Model 113. In general, the
procedure should be performed after inspecting the instru-
ment for shipping damage (any noted to be reported to the
carrier and to Princeton Applied Research Corporation),
but before using it experimentally. Should any difficulty be
encountered in carrying out these checks, contact the
factory or one of its representatives.
2.2 EQUIPMENT NEEDED
(1) General purpose laboratory oscilloscope.
(2) Signal
generator capable of providing a 1 V pk-pk
sinewave
at 1 Hz, 100 Hz, and 1 kHz.
2.3 PROCEDURE
(1) Make sure the rear-panel slide switch is in the position
indicating
the line voltage to be used (115 V ac or 220
Vac).
(2) Plug the line cord into the rear of the instrument and
into the power receptacle.
(3) Press
the power switch so that it remains depressed.
(4) Push
the spring-loaded battery test toggle to the left,
then push it to the right. The green indicator should
light for
both positions.
(5) Make
the following initial control settings:
(a) Gain:
x10; Cal.: fully counterclockwise (turn
until the switch "clicks").
11-1
(b) Coupling: A input AC, B input GND.
(c) Low
Frequency Rolloff control: 1 Hz.
(d) High
Frequency Rolloff control: 1 kHz.
(6)
Connect the oscilloscope to the output BNC jack_
(7)
Set the signal generator to 1 Hz, 1 V pk-pk, and
connect it to the A input BNC jack. (Use the
oscilloscope to make the signal generator amplitude
settings, to obtain consistency between input settings
and
output readings.)
(8) Monitor
the output; the output level should be 7 V
pk-pk.
(9)
Set the signal generator to 100 Hz, 1 V pk-pk. Monitor
the output; the output level should be ten times the
input level.
(10)
Set the signal generator to 1 kHz, 1 V pk-pk. Monitor
the output; the output level should be 7 V pk-pk.
(11) Press
the OVL recovery button; the output should
decrease
to a low level, typically 50 mV. However, the
absolute signal amplitude can vary considerably from
unit to unit.
(12) Return
the power switch to the OFF (out) position.
This completes
the initial checks. If the instrument per-
formed
as indicated, one can be reasonably sure that it is
operating properly.

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III NOLLOHS
SECTION III
OPERATING INSTRUCTIONS
3.1 INTRODUCTION
To obtain optimum performance from the Model 113, care
must be exercised in selecting the signal source impedance,
in selecting the bandwidth, and in ground loop considera-
tions, all of which are discussed below.
Fundamentally, the instrument is powered as required
either from the self-contained batteries or from the ac line,
and the signal to be amplified is applied to the input
connector(s); the amplified signal is available at the output
jack through a resistance of 600 ohms.
NOTE: Before operating from ac line power, make sure the
rear-panel switch is in the position indicating the line
voltage
to be used, and be sure the proper size line fuse is
installed (1/16 A for 115 V operation or 1/32 A for 230 V
operation). Operating from too high a line voltage will blow
the line fuse and possibly damage the power transformer
and circuit components.
3.2 NOISE AND SOURCE RESISTANCE
Best amplifier performance is often regarded to be realized
under those conditions where it least decreases the overall
signal-to-noise ratio. In
many instances the thermal noise
generated by the signal source resistance is the dominant
factor in determining the input signal-to-noise ratio. In this
respect, amplifier noise
performance can be specified by the
amount of noise the amplifier adds to the amplified source
thermal noise; expressed in decibels, this is called the
"Noise Figure":
(1) Noise Figure =
20 I total rms noise voltage at the amplifier output
0910 gain x source thermal noise voltage (rms) dB
where the Source Thermal Noise = V4KTRl'lf volts
rms =E,
and
K = Boltzmann's constant, 1.38 x 10-
23
joules/K
T =
absolute temperature in kelvins
M = equivalent noise bandwidth in Hz
R = source resistance in ohms (differential source
resistance for Model 113; if used single-ended, set
the coupling selector for th.e unused input to
ground, and regard this part of input resistance to
be zero).
The total output noise may be converted to an equivalent
input noise by dividing by the amplifier gain. The noise
figure,
expressed in these terms, becomes:
(2) Noise Figure =
20 I total rms noise voltage referred to amp. input dB
0910 source thermal noise voltage (rms)
II 1-1
Each amplifier has its own characteristic noise figure, which
varies as a
function of frequency and source resistance.
These figures are
obtained experimentally, and plotted
graphically. Figure 111-1 is a typical set of noise figure
contours for the Model 113.
30dB
--'_---l,
10 -1 10-
1
00
IO~ ~ IO~
FREQUfNr i .N Hz
Figure 111-1. TYPICAL NOISE FIGURE CONTOURS
FOR THE MODEL 113
In using these contours, the total equivalent rms input noise
is usually the quantity of interest. This can be obtained
from the graph and equation (3):
(3)
Total equivalent rms input noise voltage =
source thermal noise x antilog NF/20 volts rms
The equivalent noise bandwidth used in determining the
source thermal noise is a function of the external circuitry
and/or the amplifier bandwidth. When operating dc coupled
(LF rolloff to DC), the equivalent noise bandwidth of the
M113 is simply the HF rolloff frequency multiplied by 1T/2.
If the LF rolloff frequency setting is other than dc, the
equivalent noise bandwidth is given by the formula:

where: uted by the transformers, the results obtained using a
transformer hardly resemble the ideal theoretical results as
f2 is the setting of the HF Rolloff Control, and to use noise figure contours and amplitude transfer curves
ENB is the equivalent noise bandwidth in Hz, predicted in the example. When ug atransformer, it is best Q
ft is the setting of the LF Rolloff Control. obtained empirically for the individual transformer. Sub
section 3.11 contains such data for the transformers.
If the two frequency settings are far apart, the equivalent
noise bandwidth to aclose approximation is simply 1r/2 33 GROUNDiNG
times the HF rolloff frequency. '
_The Model 113 is specifically desi ned to have ahi hde ree
Sup.hOSe_ one _ihtehded tO_ Operate the Modei its ih of immunity to the effects of gtiound-loop curretnts. itfhe
con unction with th..-. .
tm ted t50 in expegmeh tatt htisehts ahsoutlge signal ground side of the input connectors is connected to
.pa_O.0 ms’ ah Suppose i‘ 'S_ h_OWh tat techassis ground through a10 ohm resistor. To maintain
information re uedf th d b l.. . . .
qir rom eexperiment is situate eow
__ground-loop immunity, avoid shorting the input grounds to
3S.ihCe. tits soutge tthetmet)hotgsegorhttiisutihe te_tt_he chassis ground at the amplifier end of the cables. To further
bo ad _dOtirie. is, eheh deg Oh, ahh W|i_Ft 'nt ti amp iliet reduce the effects of ground-loop currents, use an input
an Wt is minimize ysettihet eto OCohtto to cable that is short and has ahigh conductivity outer
dc and the HF toiiott ‘?°"‘F'°' to 3kH,Z' DC Coupling is used‘ conductor. (For adiscussion of the circuit desi nwith
9
h: . . ..
Tesource thetmai noise ih this Case is respect to grounding considerations, see Section IV).
E=\/4x1.38 >< 10-” X2.9x 102x 50>< 3X103X1.57
=6iXto-s Vrms CAUTION: The power rating of the 10 ohm resistor is %
iwatt. Avoid excessive ground-to-ground current to avoid
From Figure lll-1, the noise figure for the Model 113 at aburning out this reststtm
center frequency of 1500 Hz and asource resistance of 50
ohms is 18 dB. Substituting these values into equation (3): when the Signet is aepned to the input via atransformer,
totai equivaient input noise operate the amplifier single-ended. That is, place one input
Z61 Xto-s Xibis/20 selector to the ground position, and connect the trans-
eieev former to the other input (ac couple); connect one
transformer lead to the outer shell of the BNC connector
Occasionally the dc component is not required, so that the and eenneet the other transformer ieed to the Center
hest heise Dettetmehee eeh he 8Chie\/ed With the help 0t eh conductor of the connector. Connecting this way avoids the
input transformer. This is possible by taking advantage of nrebiem Qt etatie energe bui|d-up at tne inputs due te no
the property of atransformer to multiply the source greund return_
resistance by the square of the turns ratio and the voltage
by the ratio. With atransformer inserted between the signal 3_4 $|G|\|AL \/()|_TAGE AND GAIN
source and the amplifier input we can increase the effective
source resistance to avalue that reduces the noise figure to
less than 0.05 dB. From Figure lll-1, the source resistance With the Vetiehie 9eih eehttei ih the eeiihtated hesitieh
should be about 1megohm. The transformer turns ratio, ieewii the hesitieh et the geih Seieetet eeetiteteiy Sets the
tor this inibedanee inerease, is W:t40_ -|-herntai gain to the indicated level. Intermediate levels of gain may
source noise at the amplifier input is equal to the noise be ehteihed ieV use et the tiheeiibteteei Vetiehie Qeih
generated by the 50 bhrn sbtiree inuitibiied by the turns control. If it is desired to accurately set an intermediate
ratio. With anoise figure near zero, the total equivalent rms ievei et geihl ephiy eh ihhtit Sighei to the ethpiitiet ihptit
input nbise is aisb edtiai to the nbise generated by the 50 and, using an ac voltmeter, proportionally adjust the output
dhrn sbtiree nitiitibiied by the turns ratio! I70 tiv rrns_ signal level to acorresponding value between the levels of
Although the numerical value of equivalent input noise is the two tixed geih 5ettih95 hteeketihg the desired 9aih-
much larger than before, the signal-to-noise ratio isisub-
stantially increased. This can be seen by considering all of
the transformed source signal voltage as appearing at the The maximum Output that the aihphtiet Cah provide is to
amplifier input terminals, because the Model 113 input t/hits pea_k'tO'heak (through 600 Ohms ihto ah Opeh Circuit)"
teeietenee is mueh ieteet than the 1meeehm etesenteei by For maximum input voltages, refer to the specifications and
the transformer; the signal-to-noise ratio is equal to the to Suhsectioh 3'i0'
maximum possible value: esig/E xantilog NF/20) Eesie/E.
In this example the transformer increases the signal-to-noise
ratio by afactor of 8. 3.5 DC ZERO ADJUSTMENT
Princeton Applied Research Corporation manufactures
transformers for use in low level, low frequency applica- The dc zero adjustment may need to be touched Cip as the
tions. Characteristics and details regarding the use of some Qeih is ehehgeti ih Dettietliet, it the ediustmeht is titst made
of these transformers are discussed in Subsection 3.11. Wheh 0Detetih9 at ei0W Qeih, t0ii0Wed ietet hV ttehstet te
Because the transformers have so much influence in high-Qeih Opetetiehi it is impetteht that the de Zero be
determining bandwidth, and because of the noise contrib- Cheeked, ahd, it heeessetV. teedlusted as required-
lll-2
where:
ENB is the equivalent noise bandwidth in Hz,
f2
is the setting of the HF Rolloff Control, and
fl is the setting of the LF Rolloff Control.
If the two frequency settings are far apart, the equivalent
noise bandwidth to a close approximation is simply 1T/2
times the HF rolloff frequency.
Suppose one intended to operate the Model 113 in
conjunction with an experiment that presents a source
impedance of 50 ohms, and suppose it is known that the
information required from the experiment is situated below
1 kHz. Since the source thermal noise contributing to the
total noise is dependent on bandwidth, the amplifier
bandwidth is minimized by setting the LF rolloff control to
dc and the HF rolloff cuntrol to 3 kHz. Dc coupling is used.
The source thermal noise in this case is:
E
=)4 x 1.38 x 10 23 x 2.9 x 10 2 X 50 x 3 x 10 3 x 1.57
= 6.1 x 10-8 V rms
From Figure 111-1, the noise figure for the Model 113 at a
center frequency of 1500 Hz and a source resistance of 50
ohms is 18 dB. Substituting these values into equation (3):
total equivalent rms input noise
= 6.1 X 10-8 X 101 8 / 20
= 0.5 pV rms
Occasionally the dc component is not required, so that the
best noise performance can be achieved with the help of an
input transformer. This is possible by taking advantage of
the property of a transforme r to multiply the source
resistance by the square of the turns ratio and the voltage
by
the ratio. With a transformer inserted between the signal
source and the amplifier input we can increase the effective
source resistance to a val ue that reduces the noise figure to
less than 0.05 dB. From Figure 111-1, the source resistance
should be about 1 megohm. The transformer turns ratio,
for this impedance increase, is VR2/R 1 = 140. Thermal
source noise at the amplifier input is equal to the noise
generated by the 50 ohm source multiplied by the turns
ratio. With a noise figure near zero, the total equivalent rms
input noise is also equal to the noise generated by the 50
ohm source multiplied by the turns ratio, = 70 pV rms.
Although the numerical value of equivalent input noise is
much larger than before, the signal-to-noise ratio is sub-
stantially increased. This can be seen by considering all of
the transformed source signal voltage as appearing at the
amplifier input terminals, because the Model 113 input
resistance is much larger than the 1 megohm presented by
the transformer; the signal-to-noise ratio is equal to the
maxi~um possible value: esig/E x antilog NF /20) .::= esig/E.
In thiS example the transformer increases the signal-to-noise
ratio by a factor of 8.
Princeton Applied Research Corporation manufactures
transformers for use in low level, low frequency applica-
tions. Characteristics and details regarding the use of some
of these transformers are discussed in Subsection 3.11.
Because the transformers have so much influence in
determining bandwidth, and because of the noise contrib-
111-2
uted by the transformers, the results obtained using a
transformer hardly resemble the ideal theoretical results as
predicted in the example. When ug a transformer, it is best
to use noise figure contours and amplitude transfer curves
obtained empirically for the individual transformer. Sub-
section 3.11 contains such data for the transformers.
3.3 GROUNDING
The Model 113 is specifically designed to have a high degree
of immunity to the effects of ground-loop currents. The
signal ground side of the input connectors is connected to
chassis ground through a 10 ohm resistor. To maintain
ground-loop immunity, avoid shorting the input grounds to
chassis ground at the ampl ifier end of the cables. To further
reduce the effects of ground-loop currents, use an input
cable that is short and has a high conductivity outer
conductor. (For a discussion of the circuit design with
respect to grounding considerations, see Section IV).
CAUTION: The power rating of the 10 ohm resistor is 'h
watt. Avoid excessive ground-to-ground current to avoid
burning out this resistor.
When
the signal is applied to the input via a transformer,
operate the ampl ifier single-ended. That is, place one input
selector to the ground position, and connect the trans-
former to the other input (ac couple); connect one
transformer lead to the outer shell of the BNC connector
and connect the other transformer lead to the center
conductor of the connector. Connecting this way avoids the
problem of static charge build-up at the inputs due to no
ground return.
3.4 SIGNAL VOLTAGE AND GAIN
With the variable gain control in the calibrated position
(ccw), the position of the gain selector accurately sets the
gain to the indicated level. Intermediate levels of gain may
be obtained by use of the uncalibrated variable gain
control. If it is desired to accurately set an intermediate
level of gain, apply an input signal to the amplifier input
and, using an ac voltmeter, proportionally adjust the output
signal level to a corresponding value between the levels of
the two fixed gain settings bracketing the desired gain.
The maximum output that the amplifier can provide is 10
volts peak-to-peak (through 600 ohms into an open circuit).
For maximum input Voltages, refer to the specifications and
to Subsection 3.10.
3.5 DC ZERO ADJUSTMENT
The dc zero adjustment may need to be touched up as the
gain is changed. In particular, if the adjustment is first made
when operating at a low gain, followed later by transfer to
high-gain operation, it is important that the dc zero be
checked, and, if necessary, readjusted as required.
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IIA
P
4
+
30.-------------,--------------,-------------,---------------
Recovery Time = time required for the
output to settle to within 1 volt of steady
state value.
25~--------------~--------------_r--------------~
Overload ~ sufficient input to saturate the
output stage of the first amplifier.
20
-:
(.)
Data taken with the input coupling switch
in the dc position.
In the ac coupling position, a 0.1 J.lF
capacitor in' series with a 100 megohm
resistor is added (RC ~ 10 seconds).
ILl
(/)
GAIN X 2K - X 10
Minimum Recovery Time is available when
the input coupling is dc and the Low
Frequency Rolloff switch set at dc.
ILl
15
::f
t=
>-
a::
ILl
>
8
ILl
a::
10
5
The OV L pushbutton provides immediate
recovery in all modes.
Absolute Maximum I nput Voltage (differ·
ential or common mode):
ac coupling ~ 115 V, 60 Hz
dc coupling ~ ±20 V
.01
.03
0.1 0.3
1.0
LOW FREQUENCY ROLL-OFF SETTING (Hz)
Figure 111-2. TYPICAL RECOVERY TIME VS LOW FREQUENCY ROLLOFF
3.6 OVERLOAD FAST RECOVERY
If the input signal exceeds the level indicated in the
specifications (Section I). the amplifier will saturate and
remain disabled until coupling and filter capacitors dis·
charge (see the recovery time data, Figure 111-2). Pressing
the spring·loaded overload recovery toggle causes fast
discharge of the capacitors so that normal operation can be
resumed immediately.
3.7 LOW-PASS/HIGH-PASS FILTERS
Series low·pass and high·pass filters are incorporated to
provide bandpass characteristics. Minimizing the bandwidth
minimizes the source thermal noise. In addition, the filters
can be used to eliminate unwanted signals (such as dc, high
frequency, or 60 Hz pickup). The following figures are
normalized amplitude and phase transfer characteristics.
If one or both Coupling switches are set to the AC Coupling
position, the LF ROLLOFF switch should not be left in the
DC p.osition. If it is left in the DC position, output voltage
111-3
offsets resulting from the input offset current (100 pA
max) may occur. At high gains, the offset could exceed full
scale.
3.8 SINGLE-ENDED/DIFFERENTIAL
OPERATION
The amplifier may be operated differentially or single·
ended. For single·ended operation, simply place the unused
input coupling switch to the ground position, and place the
signal·input switch to ac or de coupling as desired.
For differential operation, place both coupling switches in
ac or dc positions or one in dc and the other in ac,
as
appropriate. The output voltage is equal to the gain times
the difference of the voltages at the A and B inputs.
Remember that the two signal grounds (tied together
internally) are connected to chassis ground through a 10
ohm resistor. For maximum ground-loop rejection, avoid
shorting the signal ground to chassis ground.

I1I
To do zero adjustment, place both coupling switches in
the ground position, set the L.F. Rolloff switch to DC, +80 .-
and set the gain switch to the position to be used. Then ~
adjust the front-panel zero potentiometer for 0Vat the +10 iiii" '*°
output. lix |
+60 iVii'30
3.9 DC ZERQ ADJUSTMENT lI
.. i1/
l.O
O6
FEout
O
IO
+20 las 1li-70
TOTAL GAIN =GAIN xFgq x}-Ee°i'-i
Ell‘! Lp Ell’! Hp +|Q ML.-. i.1 .-80
||l|i:1
illl2I
Ind-I'4IAIII—
)
LEAD
+OI o
J__
viaoo
EESLAG
oscnezs
+3! Q
E
oscn
+30 12- ~.,4 »1-» -T »~60
ii I
.l.1 __ .
Q.l. .,l_l i-90
Ol .lO l.O l0.0 IO0.0
IIIIIIIIIIIIIIIIIII ff
T-- 0. --
IIIIIll||IIIIln|| fme Mme
L
'(READ LEFT DEGREE SCALE) (READ RIGHT DEGREE SCALE)
0,3 i_--'"|i1—---in tom. Pans: =ALGEBRAIC suu or HF aLF PHASE ANGLES
lllllii
_
\-
'-1
--
‘s
IIII
SDcF"FF“liF||||lm|
IIIIIIIll __ll 6
‘HF sue
LIIIII
||III'nn|
_--_---II_I---IIIIIII
.llII
_--I
__—-iiii
--III-IIIII
_-
IIiV
I1||llIIIIII:::_-IIiiii ||||llIIIIII::::-III——II
l0.0
L.__i____________ ____.
Figure Ill-3. LP FILTER NORMALIZED AMPLITUDE
"TRANSFER CURVE
ii
Figure Ill-5. LP/HP FILTER NORMALIZED
PHASE TRANSFER CURVE
.._......... "-—-——_————-1
--It T'
—IIIIl—II_II§l!—II-IIIII I40 as ..._ _
-IIIII_---IIII|._---IIIII »,
_IIIIl:-I_IIIIlilI_IIIII
_IIIIl——I_IIIIl—I§:!lIIl
I00 l3OdB _
I20 dB
NdB
"lOdB
REJECTON
O68» _
commonMODE
w6
O68
aoaai -~-
:01 2 5 io‘ 25io‘ 25io° 25io°
FREQUENCY IN Hz
S
IIIll
-11-IIIIl—IZ-III I
_-I_IIIII__'l_III I
Illl III
E!!!!::::2:4!!:‘
_—--IIIIl'I—--
IIIIII_II!=l
I-IESIII -
_I-IIIIl_-
.O. I
illN
*IIIIIIIIIIIIIII
IIIIII
-EIEEIEIB
Oll|l‘ll'
IIIIIIII
IIIIIIIIIII IIII
ll|l|IIIIl|l|iIII::'-all—‘ Figure Ill-6. TYPICAL COMMON MODE
n|||IIIInuiIw.--nun
Illl||IIIIIll||I'IIIl|l|| REJECTION CHARACTERISTICS
I-=iiIiIII===iIiIl—.‘-iiiiii:
°~8 IIIIIIIIIIIIIIIIMIIIIIIun '
IIIInu||IIIIIln|rII-Innu
IIIIIIIIIIIIIIIIIIIIIIll|||
IIIIn|||IIIIIllnII-cum
O6IIIIIIIIIIIIIIIIIIIIIIlln
iiII=::::::II=:'§::i--'
E9”’ IIIIIll||IIII,:|l
Ein Hp IIIIl||||IIIIAll
0,, IIIIIIIIIIIIIAIII gggg 3.10 MAXIMUM INPUT SIGNAL CONSISTENT
:::: WITH LINEAR OPERATION
nu
IIII
iii! ----
nu When speaking of the maximum input that can be applied,
adistinction must be made between common mode signal,
::: that signal which is common to and identical at both the A
"' and Binputs, and differential signal, that signal which exists
'°° between the in ut th t'th t' med tn'n ut
T__' '- ps, ais,ais easur aoeip
U3“ with respect to the other. Aperfect amplifier responds not
at all to common mode signal, that is, if both the Aand B
inputs are driven by the same large signal, no trace of that
Figure |||_4_ HP HL-I-ER NQRMAUZED signal should appear at the output. The signal at the output
AMPLITUDE TRANSFER cunvE should result from the differential input signal only. Real
Ill-4
;l
3.9 DC ZERO ADJUSTMENT
To do zero adjustment, place both coupling switches in
the ground position, set the L.F. Rolloff
switch to DC,
and set the gain switch to the position to be used. Then
adjust the front-panel zero
potentiometer for 0 V at the
output.
TOTAL GAIN
0.6
~
~LP
0.4 f:=--
0.2
o
0.1
GAIN x jEout I x ~
E ,n L P [E;;;I HP
1.0 10.0
figure 111-3. LP FILTER NORMALIZED AMPLITUDE
TRANSFER CURVE
0.8
0.6
I
~
E in IHP
0.4
0.2
o
.01 0.1 1.0
Figure 111-4. HP FILTER NORMALIZED
AMPLITUDE TRANSFER CURVE
100
10.0
111-4
140 dB
130 dB
120 dB
IIOdB
IOOdS
90dB
80 dB
..i.." _f
fL F3dB fHF3dB
(READ LEFT DEGREE SCALE) (READ RIGHT DEGREE SCALE)
TOTAL PHASE =4LGEBRA'C StM CF HF 6 LF PHASE ANGLES
Figure 111-5. LP/HP FILTER NORMALIZED
PHASE TRANSFER CURVE
......
'"
"
c- --
"\t-,.
"\
r\.
~
.-
r--
.. -
-
~
r\.
I--
-
[1]
"
'-;-
.
'0 2 10
10' 2
10
FREQUENCY
IN Hl
Figure 111-6. TYPICAL COMMON MODE
REJECTION CHARACTERISTICS
3.10 MAXIMUM INPUT SIGNAL CONSISTENT
WITH LINEAR OPERATION
When speaking of the maximum input that can be applied,
a
distinction must be made between common mode signal,
that signal which is common to and identical at both the A
and B inputs, and differential signal,
that signal which exists
between
the inputs, that is, that is measured at one input
with respect to the other. A perfect amplifier responds not
at all to common mode signal, that is, if both the A and B
inputs are driven by the same large signal, no trace of that
signal should appear at the output. The signal at the output
should result from the differential input signal only. Real
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amplifiers, including the Model 113, do not exhibit com-
plete
immunity to common mode signals_ However, as
stated in the COMMON MODE REJECTION specification
the
immunity, though finite, is very great indeed. Thi~
immunity only holds for common mode signals of 1 V rms
or
less. With higher common mode signals, input circuits
become non-linear and a very great degradation in
common
mode signal rejection occurs. This is the meaning of the
Common Mode Maximum Input Signal specification.
To appreciate the meaning of the Differential Mode
Maximum Input Signal specifications, it is necessary to
distinguish between attenuated differential input signal and
unattenuated differential signal. Attenuated input signals
are those at a frequency which
is attenuated by either the
High
Pass Filter or the Low Pass Filter_ The frequencies
affected
by these filters depend on the setting of the
corresponding Front-panel switches. Unattenuated signals
are those at a frequency which is unaffected by the filters.
The
maximum output capability of the Model 113 is 10 V
pk-pk. Clearly, for an unattenuated signal, the maximum
differential input one can apply is 10IG V pk-pk, where G
is the selected gain. At frequencies where the filters begin
to have some effect, greater differential input signals can be
applied. The further one moves into the region of filter
influence, going either higher or lower in frequency, the
larger
the differential input signal can be. However, a limit
is reached where any further increase in· input signal,
regardless of frequency, will cause non-linear operation and
performance degradation_ This
limit, which is a function of
the Gain switch setting, is given by the two Differential
Mode Maximum input signal specifications. For gains of 10
to 100, the absolute maximum one can apply is 1 V pk-pk.
For gains of 200 to 10,000, the absolute maximum
differential signal one can apply is 100 mV pk-pk. It should
be clear that if the frequency component of interest is not
being maxima!ly attenuated by the High Pass or Low Pass
Filter, the maximum input will be lower. Figure 111-7
illustrates these relationships.
c:
>
oK
...
I
LOW FREQ.
ROLLOFF
LIMIT FOR UNATT£NUATED
SIGNALS (GAIN' 100) AS
DETERMINED BYiG
~ 10mV~--------~~~~-L------------~
Figure 111-7_ MAXIMUM DIFFERENTIAL INPUT TO MODEL 113
111-5
3.11 BATTERY OPERATION TEST
AND CHARGI
NG' ,
The Model 113 has rechargeable batteries good for up to 30
hours of operation when fully charged. If they are not fully
charged, or if the Model 113 is driving a load having an
impedance of less than 10 kS1, a shorter operating period
will result. To operate from battery power, set the Power
switch
to ON, but do not plug in the line cord. When the
period of battery powered operation is completed, be sure
to set the switch to OF F to prevent running down the
batteries.
To check the batteries, push the spring-loaded test switch
to the left and to the right. If the green indicator lights, the
corresponding battery is charged. If it remains out, the
batteries need charging.
Battery charging takes place when-
ever the Power switch is set to OF F with the Iine cord
plugged in. Beginning
from the fully discharged state, it
takes anywhere from 24 to 36 hours to fully recharge the
batteries. In general, one should follow each period of
battery operation with a charging period of equal or greater
duration.
NOTE: When the power switch is set to ON with the line
cord plugged in, the batteries
"trickle charge" at a rate very
much lower thal1 that obtained with the switch set to OFF.
For this reason, it is better to charge with the switch set to
OFF.
The batteries used in the Model 113, should they require
replacement,
can be ordered from Princeton Applied
Research Corporation. The part number is 4000-0016-04
Specification #710311 A. '
When the batteries
are being recharged (instrument plugged
in but with Power switch in OFF position), there is no time
limit, that is, there is no possibility of overcharge with
subsequent battery damage due to the charging being
maintained
for too long a time.
3.12 RACK MOUNTING
The Model 113 may be mounted in a standard 19" relay
rack, either singly
or two units side by side. The following
mounting accessories are available from the factory:
Single mounting: Panel, rack mounting, part number
1415-0553-08
Double (side-by-side)
mounting:
Coupling, rear, part number 1415-0555-14
Coupling, front, part number2517-0217-19
Screw, coupling, part number 2517-0218-18
Flanges are required for both types of rack mounting. Most
units
are shipped with the flanges, but if the unit to be
mounted does not have them, order part number
1402-0008-20 (two for each type mounting).

3_13 USING ASIGNAL INPUT Figure lll-9A is afamily of amplitude transfer curves
TRANSFQRMER for atypical Model AM-1 wired for a1:100 turns
ratio, and Figure lll-9B is the corresponding family of
HOW aSigna| input transformer can improve |OW_nOise noise figure contours. In the transformer-amplifier
performance was discussed in Subsection 3.2. There it was system’ the noise ngure ootenneo _nonn n|'9B ore"
indicated that atransformer often has abandwidth narrow demmetesl ad. Therefore, this noise -figure can be
compared with the amplifier it is being used with, and that regarded as tne system overen no'se n9ure' HoWe_Ver'
the transformer adds its own noise to the total noise. For the nansformee frequency response and tne amonner
this reason, it is best to have noise figure contours and response set Yvnn tne ronon eontro's must be eom'
amplitude transfer curves for the transformer. Princeton o'neo to ootem tne system overen response enereeter'
_I
Applied Research Corporation manufactures three mag 'st'es'
netically shielded signal transformers that may be used with
the Model 113: the Models AM-1, AM-2, and 190. Data for
each of these transformers follows. §lso ,,‘,§‘, 283222 _-_
_
"42 IOOQ SOURCE —**
(1) Model AM-1 3.1,. ._l- \
Zso _L \
Ageneral-purpose frequency response and changeable F
turns ratio render the AM-1 the most versatile of the
three transformers. NOTE: The outer connector, as
the transformer comes from the factor is wired for a/\
'IO 25IOe 25IO3 25IO‘ Z
I
Eour/EuTUR
35000 SOURCE ' ' ''''"‘I’
m
R§
-DLIQQQ
ooooo \\\- \
I‘.
I/
,'"’ \\ \
.w»~.. \l
differential output with separate ground return (see F"E°“E"°*
Figure Ill-8A). When using the transformer with the
Model 113, one half of the secondary will be shorted Figure |||-9A_ FREQUENCY RESPQNSE QF TYP|CA|_
to ground, if the Model 113 is operated single-ended as MODEL AM-1 TRANSFORMER
recommended in Subsection 3.3, unless the output
connector is rewired. To use the full 1:100 turns ratioIFrom Figure lll-9B, for aturns ratio of 1:100, the
rtne Center tap W're must be removed from p'n Ioptimum source resistance is between 10 and 100
(ground), and the wire going to pin 3removed from ohms. If asource resistance in another range is to be
pi" 3and reeenneeted to pl" 1' as shew" In Figure used, the operator may consider changing the turns
I“'8B- ratio to shift the lowest noise-figure resistance range to
that being used. The source resistance scale of Figure
lll-9B should be multiplied by the factor 104N2,
mm ourrur mm moo outrur where Nis the step-up turns ratio being used.
||: gRequired wiring and scaling information is given in
1- -Q» ‘I Figure Ill-10.
SCI-IEMATIC OF UNMOOIFIED SCHENATIC OF MODIFIED
AM—I AM-1
INPUT OUTPUT mnur OUTPU1’
ll ILAC
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INTERNAL COM£CTIONS INTERNAL CONKCTIONS
OF OF |O-I ..I5dB
LMMODIFIED AM_I MODIFIED AM-1
AB
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SHIELD SNIIID SHIELD SNIHD /\/~ I
lonmsSTANCE
SOURCERES
5OO~;_;.;.¢..§f§:§§§§5i§§§§55§55;Z~E?’fifffjffeiIf_ifififffifijfffjfj; 3dB
check “frequency response curves
above before operating in shoded‘f§§§§§§;'§§§§§i
2355557.-;§;1;§:~;§;§. ‘e9'9":
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ads-ii
-'| l5_dBl
lOdB"'r“"*'-——'
1
r
l0 I02 |o3 lo“
FREQUENCY (Hz)
Figure Ill-8. MODIFYING THE AM-1 TRANSFORMER Figure III-9B. NOISE FIGURE CONTOURS FOR
FOR USE WITH THE MODEL 113 PREAMPLIFIER TYPICAL MODEL AM-1 TRANSFORMER
6
3.13 USING A SIGNAL INPUT
TRANSFORMER
How a signal input transformer can improve low-noise
performance was discussed in Subsection 3_2_ There it was
indicated
that a transformer often has a bandwidth narrow
compared with the amplifier it is being used with, and that
the transformer adds its own noise to the total noise. For
this reason, it is best to have noise figure contours and
amplitude transfer curves for the transformer. Princeton
Applied Research Corporation manufactu res three mag-
netically shielded signal
transformers that may be used with
the Model 113: the Models AM-1, AM-2, and 190. Data for
each of these transformers follows.
(1) Model
AM-1
A general-purpose frequency response and changeable
turns ratio render the AM-1 the most versatile of the
three transformers. NOTE: The outer connector, as
the transformer comes from the factory, is wired for a
differential output with separate ground return (see
Figure 11I-8A). When using
the transformer with the
Model 113, one half of the secondary will be shorted
to ground, if the Model 113 is operated single-ended as
recommended in Subsection 3.3, unless the output
connector is rewired. To use the full 1: 100 turns ratio,
the center tap wire must be removed from pin 1
(ground), and the wire going to pin 3 removed from
pin 3 and reconnected to pin 1, as shown in Figure
111-8B.
SCHEMATIC OF UNMODIFIED
AM-'
I NTERNAL CONNECTIONS
OF
UNMODIFIED AII-'
A
SCHEMATIC OF MODIFIED
AM-'
IlfttUT
OUTI'UT
INTERNAL CONNECTIONS
OF
MODIFIED AM-'
B
Figure 111-8. MODIFYING THE AM-1 TRANSFORMER
FOR USE WITH THE MODEL 113 PREAMPLIFIER
111-6
Figure 111-9A is a family of amplitude transfer curves
for a typical Model AM-1 wired for a 1:100 turns
ratio, and Figure 111-98 is the corresponding family of
noise figure contours. In the transformer-amplifier
system, the noise figure obtained from 111-98 pre-
dominates, and, therefore, this noise 'figure can be
regarded
as the system overall noise figure. However,
the transformer frequency response and the amplifier
response set with the rolloff controls must be com-
bined
to obtain the system overall response character-
istics.
g 430
~ 420
2 ttO
....
: tao
'" 90
z
~ 80
!: 70
~ 60
'- .0
g 40
'"
tnSOURCE --
ton SOURCE - -
toon SOURCE - --
~oon SOURCE········
...
"
"
"
[,/
3°'0
...
.
/
L--
\
---
--
\
....
,
...
......
,
• '0
,
.0
.
FREOUENCY
Figure 111-9A. FREQUENCY RESPONSE OF TYPICAL
MODEL AM-' TRANSFORMER
From Figure 111-98, for a turns ratio of 1:100, the
optimum source resistance is between 10 and 100
ohms. If a source resistance in another range is to be
used, the operator may consider changing the turns
ratio to shift the lowest noise-figure resistance range to
that being used. The source resistance scale of Figure
111-98 should be multiplied by the factor 10
4 N2 ,
where N is the step-up turns ratio being used.
Required wiring
and scaling information is given in
Figure 111-10.
50°r=~r=~~==~~~~~3~d~B~~~~~
che ck frequency response curv es
'" abov e before operating in shaded .
o region .
~ 10 2 ~~~ =- tr--~~~====~dB~====~~
IdB
3dB
B
10dB
I0-1 L. ___ -'--~::::::=:::::±==
15dB
10 10 2 10 3
FREQUENCY (HZ)
Figure 111-9B. NOISE FIGURE CONTOURS FOR
TYPICAL MODEL AM-1 TRANSFORMER
)

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Sch e ma tic o f Mo del ~1 -1 T ra ns form e r, sho lolIl
fo r 1:100 t u r ns rat i o .
Th e pr i m ar y m ay be rewir ed for ot her t u rn s ratios as fol lo l.'s:
Tu rns Ra t io (lI S ) Op t
imun Sourc e R Co nn ect In pu t To Tie
51. 1 --
-------- - ---- - 120 ohms 1 ,4 ,-
59 . 7
----------- --- -- 80 1 ,10 2 -
72 . 3 --
----- - ------ - --
60
9 & 10 ,-
7 9.3 - ---- ------- - --- 50 1 ,4 9 -3.
1e 2 -- -- ---- ------ -- 30 1 , , 1 - 3.
145 ---
---- - ------ --
13 9 ,, 9 -
3.
177
--- ---- -- -- --- --
9 1 , 4 9 -
354 -
-- - ------- ----- 2.5 1 & 9 9 -4 .
Figure 111-10. SCHEMATIC OF MODEL AM-l
TRANSFORMER (UN-MODIFIED)
3
3
J
2
2
2
10
1
-
10
-4
-10
-10
An output cable, made up with connectors, and an
input connector are supplied with each AM-1 manu-
factured. When ordering the
transformer remember to
specify which instrument it is to be used with , so that
the proper connector can be provided at the amplifier
end of the cable. When making up cables for connect-
ing
to the input and to the output, use Cannon brand
audio connectors
type XLR-3-11C or XL-3-11C, or
equivalent. Coaxi al cabIe sh ou Id be used, preferably of
short length and of the low-noise variety (Amphenol
RG/U type 21 -537 or 21-541). Figure 111-8B indicates
that the center conductor of the output cable should
be wired to pin 2 and the shield wired to pin 1. A BNC
connector should be installed at the amplifier end of
the cable.
Note the resonance peak at the high frequency end of
the transformer response curve (Figure 111-9A). If the
input signal has frequency components in this range
the ampl
ifier may b~ prematurely overloaded by them,
particularly at high signal or gain levels. If high
frequency signal components
cause such problems the
operator may consider prefiltering the signal or chang-
ing the source impedance
to flatten the response curve
in this range.
CAUTION: Be careful to avoid applying a signal to the
primary such that will cause insulation breakdown of
the secondary or damage to the input circuit of the
amplifier.
CAUTION: Avoid passing excessive dc current
through the primary of this transformer. More than
200 /lA will nagnetize the core. Core magnetization
will cause thE transformer to saturate prematurely for
one polarity f ac signal, resulting in distortion of high
level signals, md a magnetized
transformer is usually
111-7
noisy and microphonic, causing low level distortion as
well. See paragraph (4) for a discussion of this
distortion and a procedure for degaussing the trans-
former. Do not measure winding resistance with an
ohmmeter; ohmmeter current is sufficient to magne-
tize
the core.
~\~~g
~ --
.-
~
- ,.. .~~ .... .--.-....
Figure 111-11. PHOTOGRAPHS OF MODEL AM-l
TRANSFORMER

(2) M°de| AM'2 wired to pin 3. ABNC connector should be installed
at the amplifier end of the cable.
The AM-2 is best for high frequency applications. The
turns ratio of this transformer is 1:100. Figure Ill-12A
is afamily of amplitude response curves for atypical
Model AM-2, and Figure lll-12B is the corresponding
family of noise figure contours. In the transformer- ®\ %1T~'§eie°>'::‘eE-cetggws 1
amplifier system, the noise figure obtained from ~
Figure lll 12B predominates, and therefore, this noise
figure can be regarded as the system overall noise '-
_ii’ —1
figure. However, the transformer frequency response 59,‘:‘
... . 9l96
and amplifier frequency response set with the rolloff é
controls must be combined to obtain the system QQ
..9°V
overall response characteristics
'5 tee in souacs —- —-
9000000000
'-I 120 50 SOURCE '¢
L
OUTPUT
/77
9no ion SOURCE ----'\ Figure Ill-13. MODEL AM-2 SCHEMATIC,
E0UT/E~TURN
QO O5 O
E100 '°°°s°°"°‘_‘;3r-" --- ...... /TURNS RATIO 1:100
'" so ,
te.to the primary such that will cause insulation break-
down of the secondary or damage to the input circuit
'/' .TF\ .". \
/-"' ’\\ 1..
VTOP,-' ,° \\'\ '._ \CAUTION: Be very careful to avoid applying asignal
40$ 2 5 10* 2 5 105 2510° O1 ‘EH6 amplifier.
FREQUENCY
NOTE: Because the Model AM-2 has aferrite core,
Fi9“'°'"'12A' FREQUENCY RESPONSE OF TYHCAL core ma netization will not occur as aresult of dc
290K
‘-
O
mu
OHMS)
RATO:00)
CERESS
TURNS
SOURCE
Z5
MODEL AM-2 TRANSFORMER g...
current. However, excessive dc current in the primary,
along with the ac signal, may result in premature
IO asaturation of the core and distortion of the signal.
(MOde|
la
wvss °°°'° °'=‘°"* °P"
IIIIIIIIIJI; ‘IjIjIjIjijIfI§5E crating in shaded region :jIjIjIjIjIjIjIjIjIjIjI'I'I'Ij._._"IjIjIjIjIjIjIjI _. "
5d
VI5The Model 190 is the best transformer to use at very
low frequencies and where good low-noise perfor-
ldB mance is required at low frequencies. This transformer
T-‘ rhas two primary windings, P1, with aP1 :P3 turns ratio
MB of 121000, and P2, with aP2:P3 turns ratio of. 1:100.
~' /Only one of these primaries should be connected at a
\eds ‘"t time, and the unused winding left open. Figure lll-15
|O-r \* /is afamily of amplitude transfer curves for the Model
03 3,rQ3 |Q4 3, Q4 |Q5 190, and Figure lll-16 is the corresponding family of
noise figure contours. The noise figure contours are
transformer-amplifier system contours, so separate
noise figures do not have to be combined. However,
FREQUENCY(Hz)
Figure Ill-12B. NOISE FIGURE CONTOURS FOR ‘the transformer frequency response and the amplifier
TYP'cA|- MODEL AM"? TRAN$F°RMER frequency response set with the rolloff controls must
be combined to obtain the overall system response
An output cable, made up with connectors, and an eharaeterietree
input connector are supplied with each AM-2 manu-
factured. When ordering the transformer remember to Note the reeenanee peak at the high frequeney end of
specm’ which i"$'"'~'me0t it is to be used With’ 5° that the transformer response curve. If the input signal has
the proper connector can be provided at the amplifier frequency eernpenente in this range the annpher may
end of the cable. When making up cables for connect- he prematureh, ever|eaded by them, partieu|ar|y at
509 T0 T09 i0PU’f 80d ‘E0 the QUTPUT, U59 (380000 bFa0d high signal or gain levels. If high frequency signal
W050 ¢0009C'E0F$ W09 X|-R'3"11C OF Xl-"3419, Or components cause such problems the operator may
eqUiVa|90'I- C08Xia| Cab|e $00U|d be Used, PF9f9rab|V Of consider prefiltering the signal or changing the source
50°" |<'-‘09'E0 30d QT the |°W'0°i$9 Va09'IV lAf0D0900| impedance to flatten the response curve in this range.
RG/U type 21-537 or 21-541). Figure Ill-13, the
schematic, indicates that the center conductor of the The geggndary winding has 3neon lamp Qgnnegted
OUTPUT Cable $00U|d be Wired Y0 D50 280d the Shield across it. If too large asignal is applied to the primary,
Ill-8
--—---.__
l
l
(2) Model AM-2
The AM-2 is best for high frequency applications. The
turns ratio of this transformer is 1: 100. Figure 111-12A
is a family of amplitude response curves for a typical
Model AM-2, and Figure
111-12B is the corresponding
family
of noise figure contours. In the transformer-
amplifier system,
the noise figure obtained from
Figure 111-12B predominates, and, therefore, this noise
figure can be regarded as
the system overall noise
figure. However, the
transformer frequency response
and amplifier
frequency response set with the rolloff
controls must be combined to obtain the system
overall response characteristics.
g L~O
::: 120
9110
....
In SOURCE --
2n SOURCE •••••••••
sn SOURCE -.-.
Ion SOURCE - ---
loon SOURCE--
71'\
_r.....;
.,"-
---
\
......
L.- -::.
;;.o.?" '· ...... 7
I- -=-
'r;;:
...
: tOO
~ 90
~ 80
I/~.· . I
/ I \ \
I
1\
.... "
-; 70
'"
~
~ 60
~
I.aJ 10'
10" 2 5 10
5
FREQUENCY
Figure 111-12A. FREQUENCY RESPONSE OF TYPICAL
MODEL AM-2 TRANSFORMER
FREQUENCY (HZ)
Figure 111-12B. NOISE FIGURE CONTOURS FOR
TYPICAL MODEL AM-2 TRANSFORMER
An output cable, made up with connectors, and an
input conne~tor are supplied with each AM-2 manu-
factured. When ordering the transformer remember to
specify which instrument it is to be used with, so that
the proper connector can be provided at the amplifier
end
of the cable. When making up cables for connect-
ing
to the input and to the output, use Cannon brand
audio
connectors type XLR-3-11C or XL-3-11C, or
equivalent. Coaxial cable should be used, preferably of
short length and of the low-noise variety (Amphenol
RG/U
type 21-537 or 21-541). Figure 111-13, the
schematic, indicates
that the center conductor of the
output cable should be wired to pin 2 and the shield
111-8
wired to pin 3. A BNC connector should be installed
at the amplifier end of the cable.
BOTH CONNE CTORS
CANNON XLR -3-9JT
Figure 111-13. MODEL AM-2 SCHEMATIC,
TURNS RATIO 1 :100
CAUTION: Be very careful to avoid applying a signal
to the primary such that will cause insulation break-
down of the secondary or damage to the input circuit
of the amplifier.
NOTE: Because
the Model AM-2 has a ferrite core,
core magnetization will
not occur as a result of dc
current. However, excessive dc current in the primary,
along with
the ac signal, may result in premature
saturation of the core and distortion of the signal.
(3) Model
190
The Model 190 is the best transformer to use at very
low frequencies and
where good low-noise perfor-
mance
is required at low frequencies. This transformer
has two primary windings, P1, with a P1:P3 turns ratio
of 1: 1 000, and P2, with a P2:P3 turns ratio of 1: 100.
Only one of these primaries should be connected at a
time, and
the unused winding left open. Figure 111-15
is a family of amplitude transfer curves for the Model
190, and Figure 111-16 is the corresponding family of
noise figure contours. The noise figure contours are
transformer-amplifier system
contours, so separate
noise figures
do not have to be combined. However,
the transformer frequency response and the amplifier
frequency response
set with the rolloff controls must
be combined to obtain the overall system response
characteristics.
Note
the resonance peak at the high frequency end of
the transformer response curve. If the input signal has
frequency
components in this range the amplifier may
be prematurely overloaded
by them, particularly at
high signal or gain levels. If high frequency signal
components cause such problems the operator may
consider prefiltering
the signal or changing the source
impedance
to flatten the response curve in this range.
The secondary winding has a neon lamp connected
across it. If too large a signal is applied to the primary,
)