Tektronix PG 509 User manual

Tektronix, Inc.
P.O. Box 500
Beaverton, Oregon
IbktfoniX’
(XiMMITTEDTO EXCELLENCE
PG 509
Pulse
Generator
INSTRUCTION MANUAL
97077 Serial Number
070-7755-00
Product Group 75 Rrst Printing OCT 1989

Copyright •1989 Tektronix, Inc. All rights reserved.
Contents of this publication may not be reproduced in any
form without the written permission of Tektronix, Inc.
Products of Tektronix, Inc. and its subsidiaries are covered
by U.S. and foreign patents and/or pending patents.
TEKTRONIX, TEK, SCOPE-MOBILE, and %are
registered trademarks of Tektronix, Inc. TELEQUIPMENT
is aregistered trademark of Tektronix U.K. Limited.
Printed in U.S.A. Specification and price change privileges
are reserved.
INSTRUMENT SERIAL NUMBERS
Each instrument manufactured by Tektronix has aserial
number on apanel insert, tag, or stamped on the chassis. The
letter at the thinning of the serial number designates the
country of manufactire. The last five digits of the serial number
are assigned sequentially and are unique to each instrument.
Those manufactured in the United States have six unique
digits. The country of manufacture is identified as follows:
B010000 —Tektronix. Inc. Beaverton, Oregon, USA
G1 00000 —Tektronix Guernsey, Ltd., Channel Islands
E200000 —Tektronix United Kingdom, Ltd., Loixlon
J300000 —Sony/Tektronix, Japan
H700000 —Tektronix Holland, NV, Heerenveen,
The Netherlands
Instruments manufactured for Tektronix by external vendors
outside the United States are assigned atwo digit alpha code
to identify the country of manufacture (e.g., JP for Japan, HK
for Hong Kong, IL for Israel, etc.).

CONTENTS
ILLUSTRATIONS Hi
TABLES iv
OPERATORS SAFETY SUMMARY v
SERVICING SAFETY SUMMARY vil
tSpecification
SPECIRCATION 1-1
INTRODUCTION 1-1
PERFORMANCE CONDITIONS 1-2
2System instaiiation
SYSTEM INSTALLATION 2-1
PREPARATION FOR USE 2-1
FRONTPANO.CONTROLSANDCONNECTORS 2-3
REPACKAGING INFORMATION 2-3
3Appiications
APPLICATIONS 3-1
SYSTEM FUNDAMENTALS 3-1
TYPICAL APPUCATION 3-3
WASNIMO I
Th» Information In tfw ramalnlng sactlons of this manual Is for quailTiad servica parsonnal only. Martotha
"Sarvlca Safaty Summary' locatad War tit this manual.
4
Theory of Operation
THEORY OF OPERATION <-1
INTRODUCTION A-1
CLOCK AND PRETRIGGER A-1
PULSE DELAY CIRCUrT 4-1
STROBE GENERATOR 4-1
OUTPUT 4-2
CHARGE UNE 4-2
POWER SUPPUES 4-2
PG 509 PulM Generator Instruction Manual I

Contents
5Performance Check Procedures
PERFORMANCE CHECK PROCEDURES 5-1
INTRODUCTION 5-1
PERFORMANCE CHECK INTERVAL 5-1
PREPARATION 5-1
CHARACTERIZATION OF THE 11801 OSCILLOSCOPE 5-2
TRANSIENT RESPONSE AND AMPLITUDE VERIRCATION 5-2
6Adjustment Procedures
ADJUSTMENT PROCEDURES 6-1
INTRODUCTION 6-1
PERFORMANCE CHECK INTERVAL 6-1
PREPARATION 6-1
POWER SUPPLY VERIRCATION/ADJUSTMENT 6-2
CHARACTERIZATION OF THE 11801 OSaLLOSCOPE 6-3
TRANSIENT RESPONSE AND AMPUTUDE VERIRCATION/ADJUSTMENT . . .6-4
7Maintenance and Diagnostics
MAINTENANCE AND DIAGNOSTICS 7-1
GENERAL MAINTENANCE 7-1
CIRCUrr BOARD REMOVAL AND INSTALLATION 7-4
SIDE COVERS 7-4
MAIN BOARD 7-4
TROUBLESHOOTING 7-4
3Options
9Replaceable Electrical Parts
10Diagrams
7
1
Replaceable Mechanical Parts
II PG 500 Pulse Generator instruction Manual

Contents
ILLUSTRATIONS
Rgure Pafle
1-
1PG 509 typical system Installation 1-1
2-
1Installation and Removal 2—2
2-
2PG 509 front panel controls and connectors 2-3
3-
1Terms used hi desoiiblnQ pulse characteristics 3-1
3-2 Rise time difference for two cascaded devices 3-2
3-
3Typical high-frec^jency distortion effect 3-3
4-
1PG 509 block diagram 4-3
6-
1PG 509 adjustment locations 6-2
7-
1Orientation arxf disassembly of multipin comectors 7—3
7-2 Troubieshooting Flowchart 7-5
PG 509 Pi^ Generator Instruction Manual

Contents
TABLES
Table Page
1-1 Electrical Characteristice 1-2
1-2 Environmental Characteristicsa 1-3
1-3 Mechanical Characteristics 1-3
5-
1Test Equipment Required 5-1
6-
1Test Equipment Required 6—1
6-
2Power Supply Verification 6—2
7-
1Relative Susceptibility to Static Discharge Damage 7-1
hr PG 509 Pulse Generator instruction Manual

OPERATORS SAFETY SUMMARY
T)ie general safety Information In this part of the summary Is for
both operating and servicing personnel. Specific warnings and
cautions will be found throughout the marxtal where they apply
and do rat appear In this summary.
TERMS
In This Manual
CAUTION statements Identify conditiorts or practices that could
result in damaige to the equipment or other property.
WARNING statements identify conditions orpracticesthat could
result in personal injury or loss of life.
TERMS
Power Source
This product is intertded to operate from apower source that will
not apply more than 250 volts rms between the supply
conductors or between either supply conductor and ground. A
protective grourxj connection by way of the grounding conduc-
tor in the power cord is essential for safe operation.
Grounding the Product
This product is grourxtod through the grounding conductor of
the power cord. To avoid electrical shock, plug the power cord
Intoaproperly wired receptacle before making any connections
to the prcxluct input or output terminals. Aprotective grourKi
corviection bywayof the grouridirig corxtuctor in the powercord
is essential for safe operation.
Danger Arising from Loss of Ground
As Marked on Equipment
CAUTION indicates apersonal irijury hazard rx>t irrvnediateiy
accessible as one reads the markinj^ or ahazard to property,
including the equipment itself.
DANGER indicates apersonal injury hazard immediately
accessible as one reads the marking.
SYMBOLS
upon loss of the protective-ground connection, all accessible
conductive parts (including knobs and controls that mayappear
to be Insulated) can rerxjer an eiectrlc shock.
Use the Proper Power Cord
Use only the power cord and connector specified for your
product
Use only apower cord that is in good conditkxi.
Use the Proper Fuse
In This Manual
This tymbol IndtoaiM where appioable oaulfotwy
or other Mormation is to be found.
To avoid fire hazard, use ortiy afuse of the correct type, vottage
rating and current rating as specified In the parts list for your
product
Do Not Operate In Explosive Atmospheres
As Marked on Equipment
DANGER-High vottage.
Toavoidexpioeion, donotoperatethis instrumentIn anexplosive
atmosphere unless it has been specifically certified for such
operattoa
Do Not Remove Covers or Panels
ProlBCllvB ground (serto) tocminal.
ATTENTION -Refer to manual.
To avoid personal irtjury, do rxX remove the product covers or
partels. Do rvX opet^ the instrument without the covers and
panels properly installed.
PG 509 Pulse Generator InstrucUon Manual V

Servic* Safety Summary
SERVICING SAFETY SUMMARY
FOR QUALIFIED SERVICE PERSONNEL ONLY
Rater also to the preceding Operators Safety Summary.
Do Not Service Alone
Do not perform Internal service or adjustment of this product
unless another person capable of rendering first aid and
resuscitation Is present
Use Cere When Servicing With Power On
Dangerous voltages exist at several points in this product To
avoid personal ii^ury, do not touch exposed connections or
components while power is on.
Disconnect power before rerrx)virg protective panels, sotderirx),
or replacing components.
Power Source
This product is intended to operate from apower source that
does not apply more than 2S0 volts rms between the supply
conductors or between either supply conductor and ground. A
protective ground oonrwction by way of the grounding conduc-
tor In the power oord is essential for safe operation.
vl PG 509 Pulaa Generator Instruction Manual

Section 1
SPECIFICATION
INTRODUCTION
The PG 509 Pulse Generator is afast-risetime puise source
ptodudno narrow rectangular pulses at arepetition rate of 50
KHz.The PG 509 can deliver acontinuous puise train at an
anplltude of 25 volts into an output load of 50 ohms.
The PG 509 Pulse Generator Is aTM 500 Series plug-in
instrumenLAtl furrctlonal electronics are irx:iuded, but It requires
Insertion In aTM 500 or TM5000 Series Power Module
Mainframe for kiterf^ng to basic power supplies.
The PG 509 Pulse Generator was primarily desigrred to be an
IntegrBl part of atest system. Figure 1-1 shows primary
components arxj connections Immediately related to the Pulse
Generator In atypical system. Other than the System Controller,
Device Under Test, artd PG 509, these are:
•Aprogrammable attenuator (TEKmONIX AT 5010, or
equivalent); used to provide system selection for the
degree of attenuation required.
•Ahigh frequerxty multiplexar/switcher
(TEKTRONIX SI 5010, or equivalent); used to route inputs
and outputs between instruments and test devices while
under system control.
Note that while the PG 509 is rK)t under direct GPIB control, it is
typically directed by Instruments that are. In amostly Tektronix
instrument configuation, this would typically mean that the
PG509 be Installed In aTM 5000 (programmable plug-in
compatible) Power Module, as is required for the other
two devices.
Standard Accessory
1Instruction martual
Figure 1-1. PG 509 typical system Installation.
PG 500 Pulse Generator Instruction Marsial 1-1

SpecifIcatJon
PERFORMANCE CONDITIONS
The limits stated In the Performance Requirements column of
Table 1-1 are valid only if the PG 509 Is operated in an ambient
temperature between 0*C anti +50*C, unless otherwise stated.
The PG 509 must be In an environment whose limits are
described under Environmental Characteristics (Table 1-2).
Allow at least 15 minutes warm-uptime for operation to specified
accuracy. 60 minutes afterstorape In high humidityenvironment.
lU>le1-1
Electrical Characteristica
Ctiaracterlstics Performance Requirements
Output Amplitude 2SVIntoS0n.
variable Amplitude Range
Front Panel Adjustment Range ±5%.
Amplitude Control Input Maximum safe input voltage ^10 V.
Input Current Output Voltage
<-0.15 mA Output Is corttroiled by the front
panel VARIABLE AMPUTUDE
adjustment
-0.5 mA 2625 V±.2%.
-1i)mA 25i»V±.2%.
-1.5 mA 23.1^ V±2%.
Pulse Output Frequerx:y 50 kHz ±.10%.
Pulse Wkjtfi 44 ns ±2 ns (measured at 50% poirts).
Puisa Disable TTL logic low to disable; maximum safe input vottage <10 V.
Rise Tima 350 ps ±.50 ps (measured at System output connector).
PRETRIGGER Out 220 mV±20% (into 50 H).
PRETRIGGER signal before PULSE OUTPUT signal 115 ns ±.25% (delay factor).
1-2 PG 509 Puiae Generator instruction Manual

Specification
Table 1>2
Environmental Charactertstica*
Characteristics Description
Temperature Meets MIL-T-28800B, class 5.
Operating 0*Cto +50»C.
Non-operating -55«Cto +75«C.
Humidity Meets MIL-T-28800B, class 5.
95% RH. 0*Cto +30*C
75%RH.to40*C
45% RH.to50*C.
Attitude Meets MIL-T-28800B, class 5.
Operating 4.6 km (15.00 ft).
Non-operating 15 km (50,000 fl).
Vibration** Meets MIL-T-28800B, class 5, when installed in qualified power modules**.
0.38 mm (0.015 in) peak to peak, 5Hz to 55 Hz. ^minutes.
Shock Meets MIL-T-28800B, Class 5, when installed In qualified power modules^.
20 g's (1/2 sine), 11 ms duation, 3shocks in each diractlon along 3ma)or
axes, 18 total shocks.
Bench Handling** Meets MIL-T-288006, class 5, whan installed in qualified power modulas^.
12 drops from 45*. 4in or equilibrium, whichever occurs first
Transportation Qualified laxler National Safe Transit Association Preshipment Test
Procedures 1A-B-1 and 1A-B-2.
EMC Within limits of FCC Regulations, Part 15, Subpart J, Class A; VDE0871; arvt
MIL-461A tests RE01, RE02, CE01, CEOS. RS01, RS03, CS01, and CS0^
Electrical Discharge 20 kV maximum charge applied to Instrument case.
^WKh povMT module.
^fleqidres retainer dip.
*Refer to TU 6000 Rmwer Module apodfieatlona.
*WWmuI Power Module.
Table 1-3
Mechanical Characteriatics
Characteristics Description
Nominal Overall Dimensions
Height 4J61 In (126.0mm).
Width 2.63 In (66.8 mrr^.
Length 11.493 in (291.9 mm).
Net Weight 2lb (0.907 kg).
Finish (front panel) Plastic/aluminum laminate.
PG 509 Pulse Generator Instruction Manual 1-3

Section 2
SYSTEM INSTALLATION
PREPARATION FOR USE
Operating Environment
The PG 509 should be operated In aclean, controlled
environmertt that does not exceed the environmental limitations
listed In Section 1, Table 1-2.
NOTE
Before Installation, refer to the Operators Safety
Summary In the front of this manual and to the
Change tnformaPon section at the rear of this
manual. Also refer to the power module Instruction
manual for line voltage requirements and power
module operation.
The instument operates in any compartment of aTM 500 or
TM 5000 Series Power Module. Referto the TM 500/5000 Series
Power Module Instruction Manuals for module connector infor-
mation, as well as details on line voltages and general power
module operatioa
The PG 509 must be calibrated in the system it will be used with.
The specifications listed in the previous section are for the
PG 509 at the system output, not at the PG 509 front panel.
Installation and Removal
Toprevertt damage tothePG 509, turn off the power
rrmdule before Installation or removal. Do not use
excessive force when installing or removing the
PG 509. Refer to the Operator Safety Summary at
the front of this manual and check the change
Information at the back ofthis manual foradditional
safety notes.
FigurB2-1 showsthe installation and removal prooedure. Check
to see if the plastic barrier on the interconnecting jack of the
selected power module compartments matches the cut-out in
the circuit board edge connectors at the rear interface.
Aligpi the chassis of the plug-in unit with the upper and lower
guiderails oftheselected compartments. Push inward arfo press
firmly to seat the circuit board edge oonnectorBin the
Inferamecting jacks.
PG 509 Pulse Generator Instruction Manual 2-1

System Installation
To remove the PG 509, turn off the power module and puli on the
release latch (front panel, lower left comer) until the
irrterconnecting jacks disengage. Pull straight forward to remove
the plug-in from the power module.
Power-Up and Front Panel Indications
Apply power to the PG 509 by activating the POWER switch on
the TM 500/TM 5000-Series power module.
There Is no Indication on the front panel that power Is applied.
BARKER
7755-01
Figure 2-1. Installation and Removal.
2-2 PG 500 Pulse Generator Instruction Manual

System Installation
FRONT PANEL CONTROLS AND
CONNECTORS
See Figure 2-2 for the PG 509 front panel controls arxJ
oomectoTB.
Connections to the front panel PULSE OUTPUT SMA-type
connectorshould be made using ahigh quality semi-rigid 50-0
coaxial cable, such as Tektronix part rxjmber 015-1015-00, or
better.
For best vswr (voltage-standing wave ratio) and maximum
power transfer oorxlitions, the signal source output impedance
should match the input load Impedance of the signal receiving
device. Unmatched source and load impedances degrade the
vswr specifications. If terminators are used, they should be
placed at the signal source or load (or both), never at the front
panel PULSE OUTPUT SMA-type connector.
7755-12
Figure 2-2. PG 509 front panel controls and connectors.
^PRETRIGGER Connector
Outputs atrigger pulse In advance of the output pulse
(from the PULSE OUTPUT connector) to properly trigger
related calibraticn equipment
^VARIABLE AMPLITUDE Adjustment
This adjustment varies the output level of the PULSE
OUTPUT connector signal.
^PULSE OUTPUT Connector
SMA-type plug-in output signal connector.
^AMPLITUDE CONTROL INPUT Connector
This connector provides ameans of controlling the output
amplitude of the generator via an kiput current sourcethat
varies between 0mA and -2 mA. For currents less than
-0.15 mA. the generator output level is controlled by the
front panel VARIABLE AMPLITUDEadjustment. This input
is also at the rear module comector.
^PULSE CONTROL INPUT Connector
This input enables or disablesthe generator outputsignal.
Whan the signal to the connector is aTTL LO, then
generator output signal Is disabled; when aTTL HI, the
generatorout^signal Is anabied. This Input is also at the
rear module connector.
REPACKAGING INFORMATION
Ifthe instrument Is to beshipped toaTektrcnix Service Centerfor
service or repair, attach atag showing:
•Owner (with address) and the name of the irvUvidual at
your firm that can be contacted
•Oomplete Instrument description and its serial number
•Adescription of the service required
If the oritfnal package is rx)t fit to use ornot available, repackage
the instnjment as follows:
•Surrourxj the instrument with polyethyiene sheeting, or
cXher suitable material, to protect the extartor finish.
•Obtain acarton of oomjgated cardboard of adequate
strengththat has inside dimensionsno less than six inches
more than the instrument dimensions.
•Cushion the Instrument by tightly packing dunnage or
urethane foam between the carton and the instrumem, on
all sides.
•Seal the carton with shipping tape or an Industrial stapler.
The carton test strength for your instrument is 200 pouTKls.
PG 500 Pulse Generator Instruction Manual 2-3

APPLICATIONS
Section 3
SYSTEM FUNDAMENTALS
Some fundamental factors to consider when preparing tf^e
PG 509 Pulse Generatorfor use Inasystemwili be covered inthis
section. These systems provide abasis for the development of
other specialized systems as required by specific applications.
Pulse Definitions
The following terms are commonly used In describing pulse
characteristics and are defined here for convenierx». Theterms
are illustrated and applied in Figure 3-1. The other waveforms
represent typical output waveforms in order to show the
relationships. The terms and their definitions are:
•Risetime V'Die time Interval during whichthe amplitude of
the output voltage changes from 10% to 90% of the rising
portion of the pulse.
•Falitimeti: The time Interval during which the amplitude of
the output voltage changesfrom 90% to 10% of thefalling
portion of the waveform.
•Pulse Width (or Duration) VThetime duration ofthe pulse
measured between the 50% amplitude levels of the rising
arxi falling portions of the waveform.
•Tilt Ameasure of the tilt of the full amplitude, flat-top
portion of pulse.Thetilt measurement is usuallyexpressed
as apercentage of the amplitude of the rising portion of
the pulse.
•Overshoot: Ameasure ofthe overshoot occuring generally
above the 100% amplitude level. This measurement is
also expressedas apercentage ofthe pulse rise.
Bear In mind that these definitions are for guide purposes only.
When the pulses are very irregular (such as excessive tilt,
overshoot, etc.) the definitions maybecomeambiguous. In such
cases, amore complete description of the pulse will probably
be necessary.
OUTPUT
OUTPUT
WAVEFORM
tre RtSETME
tfs FALL TIME
tws PULSE WIDTH
%TILT »|-X 100%
%OVERSHOOTs ^X100%
775503
Rgure 3-1. Terms used In describing pulse characteristics.
P6 509 Pulse Generator Instruction Matuial 3-1

Applications
Rise Time
The rise time of any particular assembly of the PG 509, an
oscilloscope (conventional or sampling), arxt accessory pieces
such as coax cables, is avariable depending upon the cable
characteristics as well as individual risetimes. The ‘root of the
sum of the square* method can generally be applied as an
approximation methodonly, as skin effect losses ofthe cablesdo
not add properly using this method. (The root-sum-squares
method applies accurately to Gaussian syrtems only.)
As ageneral njle. If the equipmentor signal being measured has
arise time 10 times slower than the PG 509 and other related
measurirtg equipment, the error Is 1%. This amount is small and
can be oonsideted to be negligible. If the equipment being
measured has arise time three times slower than the related
measuring equipment, the error Is slightly less than 6%. By
keeping these relationships in mind, the results can be
interpreted intelligentiy.
Waveforms
The Illustration shown in Figure 3-2 can be used as aguidelirre
for the tbilowing general considerations:
•Oscilloscopesshould have avertical system rise time
about orre-seventh of the fastest signal applied to keep
system errors to aminimum. Corrversely, If the signal rise
time is at least seven times faster than the rise time of the
osciliaecope vertical system, the displayed (observed)
waveform will have arise tirrre that Is very doseto the rise
time of the vertical systent
•The (Ssplayed rise time is related to total system
bandwidth. Asystem with limited high-fraqiancy
response will produce adisplayed rise time that is slower
than expected. If afast-step signal produces acrt display
with little or not overshoot or ririging, the product of
oscillosoope risetime aixl osdlloGCope bandwidth should
result inafactorwhosevalue lies between0.329 andO.350.
Figure 3-2. Rise time dNferenee for two cascaded
devices.
3-2 PG SOS Puise Generator Instruction Manual

Applications
Rgure 3-3 illu^rates waveform distortion due to Incorrect
high-frequency compensatiorrs. Ringing indicates incorrect
peaking adjustments or undesired irxjuctlve effects. Excessive
overshoot and rolloff Indicates Incorrect capacitive adjustments.
Limited high-frequerx:y response is also indicated by rise time
measurementsthat are much slower than expected. Impedance
mismatching will usually show up as excessive aberrations
somewhere along the fiat portion of the waveform.
Figure 3-3. Typical htgh-frequeney tfatortton effecL
•Shield measuring equipment leads to prevent undesIred
coupling to other parts of the circuit. Shielding is especial-
ly required where radiation is aproblem and where
high-impedance dividws or circuits are involved.
•Chooee components which function properly at frequerv
des arxJ rise times encountered.
•Keep kt mind Inherent parameters in circuit components
such as Irxjuctance present in capacitors or resistors.
•Oonsider the possible nonlinear behavior of ctrcuit com-
ponents due to changes in voltage or temperature
coefficiants.
•Consider the input impedance of measuring equipment
The impedarx» may be enough to cause loading effects,
detunirig, or undesirable reflections.
TYPICAL APPUCATION
Measujins OUT Rise Time
The PG 509 can be used In conjunction with an oscilloscope to
determine the rise timeof aDevice UnderTest (DUT). Risetime is
rarmaily measured between the 10% and 90% am^ltude levels
on the ieadng edge of awaveform. The rise time of acfisplayed
waveform is shown in Figure 3-1.
Before measuring the rise time of adevice under test the
combined rise time of the PGS09 ou^tut signal and the
oscillcecope verticai amplifier system must be known. Refer to
Figure 3-1 tor the percerttage errorto be expected whenthe two
devices are cascaded. For example, a2-ns oscilloscope
monitoring a10-nssignal (5:1 ratio) would permitanobeervation
error of 2%. Note that if the rise times are equal, the error Is
41.4%.
Basic Precautions
Forfaithful reproduction of the pdee, certain precautionsshould
be followed. These are summarized below:
•Use propertypes of cables, terminations, attenuators, and
impedam matching networks. Low-Impedance coaxial
cablesare used with the PG 509 as signal conductors. It is
important that these cables be terminated in their
characteristic Impedance (50 ohms) to prevent reflections
arxj stancflng waves unless you dellberatsly wish to
Improperly tarminats the cables. One application tor
improper termination would be to boost the signal to an
amplifier Input by leaving the end of anansrTtisslon lina
irterminated.
•Keep unshielded wires of uncertain impedarK» short so
that reflection arxl/or cross-coupling Elects are not
introduoed. Keep ground-return paths short and dired
PG 509 Pulse Qerterator Instruction Manual 3-3

THEORY OF OPERATION
Section 4
INTRODUCTION
This section [xovides adiscussion of the nnajor elements
Incorporated in the schematic for the PG 509 Pulse Generator.
The circuit consists of six major elements; Clock and Pretrigger.
Pulse Delay, Strobe Generator, Output Pulse and Regulator,
Charge Line, artd Power Supplies. An illustration showing the
relationship of the circuit elements, as well as major control and
output locations, is provided in Figure 4-1.
The PG 509 Pulse Generator produces narrow, fast rise,
rectangular pulses at arepetition rate of 50 kHz. The method
used in this generator char^alength of coaxial cable which is
then switched to the 50-ohm load with atransistor switch
operating in avalanche mode.The charge line contained within
the unit develops apulse width equal to twice the electrical
length ofthe line. Fbrthe model, this width isequivalentto44 ns.
The nominal output amplitude of the pulse is 25 Vinto 50ohms.
Afoldout schematic is located In the Diagrams section near the
back of this manual. The following paragraphs descrftie the
individual elements.
CLOCK AND PRETRIGGER
Transistors Q30 arxJ Q35 form aSchmitt Oscillator producing a
low-dutycycle, pxisitive-going pulseat the collector of 030. The
repetition rate is set by 040, a0.9 mAcurrent source, and C28, a
0.1)iF capacitor in 040’s collector. Apositive-going ramp of
approximately 2volts Is supplied to the base of 035,turning it off
when the base goes more positive than the base of 030. The
voltage step at the collector of 030 turns 045 on, discharging
C28, resetting the Pretrigger Schmitt, andsupplyingapuisefrom
the emitter of 045 to the Pretrigger Schmitl circuit
The Pretrigger Schmitt circuit 050 and 058, outputs apositive
voltage pulse of 220 mV at J55 into a50-ohm load and a 2 V
pulse to the arxxle of CR20. The purpose of this circuit Is to
supply atrigger pulse In advance of the output pulse to properly
trigger calibration equipment
PULSE DELAY CIRCUIT
The positive going Pretrigger pulse turns off 060 and 065. This
allows C25 to start charging in anegative direction. When the
voltage becomes sufficiently negative to turn on CR16, the
current from currerrt source 070 is switched to 075.
Theresistorchain in the base of 075 determineswhere 075turns
on, and therefore the time after the Pretrigger pulse. This
provides anominal delay of 115 ns. Apulse is coupled from 075
to the base of 080 through traristorrnerTZ turning on 080. The
negative portion of the Pretrigger pulse at the arxxle of CR20 is
zero voits. This allows 060 to oorxluct. turning on 065 which
discharges C25arxl resets thedelay circuit DiodesCR17, CR1
8
arxt CR19 prevent 065 from saturating, thereby errsuring a
fast turn-off.
STROBE GENERATOR
Transistors 083arxl 090form aregulated powersuppiyfromthe
150 Vunregulated input This is used to supply -MlOvoltsto
the collector of 080 which Is biased to operate in the
avalarx:he mode.
Transistor 080 will avalanche whan apulse from T2 fonward
biases its base-emitter jiaxrtion. Capacitor C20 is then dis-
charged through R64, R99, and the primary ofT1 .This produces
avoltage in the secorxlary which is sufficient to forward bias the
base-emitter jurxffion of Q100, the output switching transistor.
PG 509 Pulse Generator Instruction Manual 4-1

Theory of Operetion
OUTPUT
Transistor Q100 is biased to operate as an avalanche transistor
switch which connects DL100, acharged 50-ohm coaxial cable
(Charge Line), into aSO-ohm load when conducting.
The output pulse Is peak detected and applied to the gate of
Q160A. It is compared with areference voltage received at the
gate of Q160B from the collector of Q210/TP1. This reference
voltage, nominally 23.4 V, can be varied by adjusting R18, the
voltage at pin 2of J25, or the current at pin 2of J5.
The amplifier consisting of transistors Q110, Q120, Q130, Q140,
Q150, Q160, and U210A adjusts the voltage at the cdiecta of
Q100 urttil the output pulse is similar to the reference from 0210.
varying the nominal -1 mA of current Input to J5 pin 2by
±.0.5 mA will vary the output voltage ±5%. Decreasing the
currenttoapproximately -0.15mAorlesswillcausetheoutputof
U210C to switch positive, turning off Q224B, disabling the Input
from J5-2/P1B-15, arrd turning on Q224A, enabling the front
panel VAFUABLE AMPLITUDE control through J25.
Transistor 0200, CR203 arKj R44 limit the maximum current that
OllOcan supply, to about 10 mA. Diode VR210.a75-voitZener,
andCRII limit the O100 collector voltage to about 100 volts In
the abserxre of an output pulse. Note that without control, the
voltage on the Charge Line center conductor can go to the
unregulated value of about -I-200V, depending on the line
voltage. Pin 1of J5 provides ameansto disable the output when
aTTL logical LO is supplied by the attenuator, AT 5010, so that
switch contacts will not be damaged as various ranges are
selected.
CHARGE LINE
The Charge Line is ahigh quality, teflon dielectric, 50-ohm
cxjaxial cable, installed in acoil within the module. The lirre is
connected to J100 at one end and left open terminated at the
other. The line has atotal physical length of approximately
15-1/2 feet and an electrical lerigth of about 22 ns. The Output
Pulse width is equal to twice the electrical length ofthe line; thus
the pulse from Q100 results in apulse width of approximately
44 ns. Capacitors C101 ,C102, and C103 are In parallel with the
Charge Line arrd are used to adjust the flatness and aberrations
of the pulse.
POWER SUPPLIES
Theurvegulated +150-Vsupply is made by connecting someof
the TM 5000 power module transformer windings in series and
then doubling the result
All other voltages used by the PG 509 Pulse Generator are
regulated onthe circuit board. Voltages used, as well asprincipal
iraegrated circuits associated with each voltage regulation, are
provided below:
U20A+9V
U20B-9V
U10A+18V
U20A-18V
4->2 PG 509 Pulse Generator Instruction Maitual

Theory of Operation
PULSE
OUTPUT
25V INTO 50Q
«iav >isv 77SS-09
Figure 4-1. PG 509 block (fiagram.
PG 509 Pulse Generator Instruction Manual 4-3