HP 460A User manual

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INSTRUCTION AND OPERATING MANUAL
FOR
MODEL 460A
WIDE BAND AMPLIFIER
Serial 1996 and Above
..
HEWLETT-PACKARD COMPANY
275 PAGE MILL ROAD, PALO ALTO, CALIFORNIA, U.S.A.
#460A004

General Description
The Model 460A Wide Band Amplifier is designed to faithfully am-
plify extremely short pulses without objectionable ringing or over-
shoot. The high frequency response matches the Gaussian curve.
A gain of 20 db is obtained with this amplifier 0 Up to five ampli-
fiers may be cascaded for additional amplification.
The Model 460A is useful as a general laboratory amplifier, to
increase voltmeter and oscilloscope sensitivity, and in television
work.
Parts Substitutions
Difficulties in procuring some of the parts used in this instrument
may cause the electrical or physical values to deviate from those
shown in this instruction manual. These substitutions have been
made so as not to impair the performance of this instrument
o
Whenever replacement of any of these parts is necessary, either
the substitute value or the original value may be used.

SPECIFICATIONS FOR c§j) MODEL 460A
WIDE BAND AMPLIFIER
FREQUENCY RESPONSE:
GAIN:
OUTPUT:
INPUT IMPEDANCE:
NOISE FACTOR:
DELAY CHARACT ERISTICS:
RISE TIME:
POWER SUPPLY:
SIZE:
WEIGHT:
High Frequency - closely matches
Gaussian curve when operating into
a lOO-ohm resistive load. 3 db point
is 140 mc.
Low Frequency - when operating from
a 200-ohm source and O. 1 ~f blocking
condenser. frequency response off
3 db at 3 kc into an open circuit or
succeeding amplifier. When operat-
ing into a 200 -ohm load, off 3 db at
100 kc.
With c§j)410B VTVM - when used with
c§j) 46A -95D Adapter. response i:1 db.
ZOO KC to 200 MC.
Approximately ZO db into ZOO-ohm
load. Gain control has range of 6 db.
Five amplIfiers may be cascaded.
Approx. 8 v peak open circuit. Output
impedance, 300 ohms.
ZOO ohms.
Less than 10 db.
Approx. .0 14 ~ sec.
Approx. . 00z6 ~ sec. (10% to 90%
amplitude). No appreciable over-
shoot.
115/Z30 v ±10%. 50/1000 CPSD 35
watts.
19" relay rack panel. 5-1/4" high;
6-3/4" deep.
11 pounds.

i
SECTION I
OPERATING INSTRUCTIONS
1-1 INSPECTION
This instrument has been thoroughly tested and inspected before
being shipped and is ready for use when received.
After the instrument is unpacked
a
it should be carefully inspected
for damage received in transit. If any shipping damage is found
a
follow the procedure outlined in the "Claim for Damage in Ship-
ment" page at the back of this instruction book.
1-2 CONTROLS AND TERMINALS
ON
This toggle switch controls all the power supplied to the instru-
ment from the powe r line.
Q)
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-:t'
GAIN
This variable resistor controls the gain of the amplifier.
FUSE
The fuseholder contains a 006 ampere cartridge fuseo The fuse
may be replaced by unscrewing the fuseholder cap and inserting
a new fuseo Replacement fuses for this instrument should be of
the llslow blow" type as specified in the Replaceable Parts Lista
INPUT. OUTPUT JACKS AND ACC ESSORIES
The input and output jacks. located on the control panel. fit special
connectors and cables which have been designed for use with Model
460A because it is not possible to obtain the best performance with
this type of device if standard commercially available connectors
are used
o
The accessories listed below are not supplied with the instrument.
These accessories are designed to solve special connection problems
likely to be encountered in the use of the Model 460A
o
The acces-
sories may be purchased from the Hewlett-Packard Companyo
cffp MODEL NO
o
46A-16A
DESCRIPTION
Patch Cord - Special 200 ohm cable two
feet in length. complete with two No. 46A-
95B Cable Plugs. for inter-connection of
two amplifiers in cascade.
-1-

~ MODEL NO.
46A-16B
DESCRIPT ON
Patch Cord - Same as No. 46A-16A
except six feet in length.
46A-95A Panel Jack - Special low capacita.nce
panel jack designed for ZOO ohm cable.
Mates with Nos. 46A-16A and 46A-16B
Patch Cords or No. 46A-95B Cable Plug.
Requires 1-1/8 inch diameter mounting
hole.
46A-95B
Cable Plug - Low capacitance plug de-
signed for use with ZOO ohm cable o Mates
with No. 46A-95A Panel Jack and with No.
46A-95E Connector Sleeve.
8lZ-5Z
Cable Special ZOO ohm cable available
in lengths to meet customer req"Girements.
The input circuit of the Model 460A is a terminated transmission
line with a characteristic impedance of ZOO ohms.
The output circuit has an impedance of Z80 ohms (resistive)o The
load impedance determines the gain of the amplifiero Therefore,
it is not necessary to match the load to the output of the amplifier
unless the gain is adversely affected. Shown below are two dia-
grams for connecting a matched or unmatched load to the Model
460A using a ZOO ohm cable.
I-'
N
-
-.D
-
11l
11l
Adapter for connection to 5XP CRTo
50 Ohm Adaptor - Provides a cyp~ N con-
nection for coupling a 50 ohm transmission
line to the input of a Model 460A amp_i£ier~
Includes a terminating resistor.
Connector Sleeve - Provides for joining
two No
o
46A-95B C3.ble Plugs in order to
interconnect two lengths of ZOO ohm cable
o
Adaptor for Model 410A/B Voltmeter
Probe - Consists of a bayonet type sleeve
with which a Model 410A/B Probe may
be directly connected to the output of a
Model 460A Amplifier
o
Includes the
proper compensating LC components.
46A-95F
46A-95E
46A-95C
46A-95D
OPERATION 1-4
-Z -

200
ohms
load
-(<e-T-(-~'~--
... 1
Model 460A
OUTPUT
Model 460A
OUTPUT
Connect across output Jack
-- inside ins rument
--<~--f(-"+-\ --+~
620 To any
ohms load
#812-52
200 ohm
cable
LO
LO
-
0'
-
N
-
The GAIN control will vary the gain of the amplifier over a ange
of approximately 6 db. This control is provided so that the gain
of the amplifier can be set to a known value if necessary. There
is no feedback in the amplifier D so the gain is directly propor-
tional to the Gm of the tubes. The gain is also determined by he
output load and will vary with output load in accordance with th
relation 280 X ZL
280 + ZL
The Wide Band Amplifier can be used with the 0jJ Model 410B*
Vacuum Tube Voltme er to provide additional sensitivity in meas-
uring high frequencies. A special adaptor is a ailable to connect
the probe of the Model 410B* to the output terminal 0 the amplifi r.
The overall frequency response of the Model 460A. in combination
with the Model 410B. is within 1 db out to 190 mc. This combI-
nation will give a full scale meter reading on the Model 410B with
1/ 10 volt applied to the input of the Model 460A.
Several amplifiers can be cascaded when more than 20 db gain is
desired. The maximum gain which can be used will be limited by
the effective noise generated in the input circuit of the amplifier.
The noise factor is approximately 10 db.
The time of rise of a single unit is approximately 2. 6 millimicro-
seconds. As units are cascaded
D
the time of rise goes up as the
square root of the sum of the squares of times of rise of he
individual stages. Therefore. for two stages in cascadeD the time
* Also Model 4l0A
-3 -

of rise will be approximately 3. 7 millimicroseconds and for three
stages, the time of rise will be approximately 4.4 millimicro-
seconds.
1-5 CIRCUIT DESCRIPTION
The Model 460A is a new type amplifier which has a very wide
transmission band. It has two stages with five tubes in the first
stage and seven tubes in the second stage. The grids of these
tubes are connected along one transmission line for the input cir-
cuit and the plates of the tube s are connected along a second
transmission line for the output circuit. A wave traveling down
the input line excites the grids in succession and half of the cor-
responding wave generated in the plate circuit travels down the
plate line toward the output and is reinforced at each successive
plate. The part of the wave in th plate line which travels in the
reverse direction is absorbed by a termination of the other end of
that line. By the time the wave in the plate line reaches the out-
put, it has been amplified by about 10 db. The second stage adds
another 10 db to make a total of 20 db gain for the unit.
The Model 460A will amplify pulses with an extremely short rise
time and with vi tually no overshoot. The time of rise of the
amplifier itself is approximately 2.6 millimicroseconds. The
amplifier has an amplitude response closely matching the Gaussian
Curve, which is the ideal transmis sion for pulse amplifications
when ringing or overshoot cannot be tole=ated.
-4-

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Curve
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Optimum
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Pulse
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100
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MODEL
460A
WIDE
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AMPLIFIER

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SCHEMATIC
DIAGRAM
OF
MODEL
460A
TRANSFORMER DETAIL
11
11''''
}>OY
II!V
WIDE BAND
AMPLIFIER
SER I
AL
19968
ABOVE