Tektronix 108 Instruction Manual
MODELS 108, 109 AMPLIFIERS
CONTEXTS
TABLE OF CONTENTS
Section
GENERAL DESCRIPTION . . . . . . .
1.
l-l. General . . . . . . .
1-2.
l-3.
1-4.
l-5. Accessories . . . . . .
l-6. Equipment Shipped . . . .
OPERATION . . . . . . . .
2.
2-1. Terminals . . . . . . . .
2-2.
2-3.
2-4.
2-5.
2-6.
2-7.
2-8.
2-9.
Z-10.
CIRCUIT DESCRIPTION
3.
3-1.
3-2.
Models 108, 109 Differences
Specifications. . . . . . .
Applications. . . , . .
Operating Procedures. . . .
Cascading . . . . . . . . .
Gains Other Than 10, 100
1000 and 10,000. . . . . .
Open Circuit Operation. . .
Amplifier Noise . . . . . .
Rise Time . . . . . . . . .
Delay Time. . . . . . . . .
Ground Loops. . . , . . .
Stray Fields. . . . . . . .
.......
General
Amplifier Design.
..........
.....
Page
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7
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Section
5-3.
5-4.
5-5.
5-6. Low-Frequency Response
6. ACCESSORIES. . . . 19
6-l.
6-2.
6-3.
REPLACEABLE PARTS. . . . . . . . . 21
7.
7-l.
7-2. How to Order Parts . . . . . 23
Models 108,
Calibration . . . 14
Model 108 High-Frcqurnc)
Calibration . . . 14
Model 109 High-Frequency
Calibration . . .
Check........... 16
Model 1081 Power Supply 19
Model 1042 Accessory Kit . . 19
Model 1082 Mounting Plate . 20
Replaceable Parts List . . . 23
Models 108, 109 Replaceable
Parts List. . . . . . . . . 24
Model 1081 Replaceable Parts
List. . . . . . . . . . . . 26
Models 108, 109 Schematic
Diagram 17971D. . . . . . . 29
Model 1081 Schematic Diagram
17966C. . . . . . . . . . 30
109 Lo\<-Frequency
Page
15
SERVICING
4.
4-1. General
4-2.
4-3.
4-4.
CALIBRATION
5.
5-l. General
5-2.
0266R
............
..........
Servicing Schedule.
Parts Replacement
Troubleshooting
...........
..........
Calibration Schedule.
.....
......
....
...
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. 13
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+ Change Notice
3~ Yellow Change Notice sheet is
included only for instrument
modifications affecting the
Instruction Manual.
Last Page
MODELS 108, 109 AMPLIFIERS
GENERAL DESCRIP'IIOS
SECTION 1.
l-l.
The Model 108 is tuned for a wideband frequency response;
response.
GENERAL.
(See Figures 9 and 10 for illustrations of the two responses.)
The Keithley Models 108 and 109 are small, 12-ounce Xl0 gain amplifiers.
GENERAL DESCRIPTION
the Model 109 is tuned ior pulse
Both
?lodels require an external power supply, preferably the Keithley Model 1081 Power Supply, which
can drive up to three of these units at one time.
a. The Model 108 bandwidth is from 1 kc to 180 MC (-3db).
150 MC is flat 20.5 db.
Voltage gain is 10 (20 db) when terminated
Response Erom 2.5 kc to
into a 50-ohm load.
Up to four Model 108 Amplifiers may be cascaded for gains to 10,000, or one may be used
with other amplifiers to increase total gain by 10.
The input impedance is 50 ohms.
Noise is less than 30 microvolts rms referred to the input.
The Model 109 Pulse Amplifier has a rise time of less than 3 nanoseconds (10:: to
b.
90%). Overshoot is less than 2%, pulse width for a 10% droop is 30 microseconds.
specifications are the same as for the Model 108. Four Pulse Amplifiers may be
for gains to 10,000,
l-2.
MODELS 108, 109 DIFFERENCES.
a. The Models 108 and 109 differ only in their tuning.
identical. Most of the Instruction Manual applies to both
or one may be used with other amplifiers to increase total gain
The circuits and the parts are
units.
Where there are differ-
Other
cascaded
by
ences - such as application suggestions and calibration - the models are identified.
10.
Specifications and operations in this
b.
PO
‘Wer
Supply to power the Amplifier. It is recommended that this Power Supblv be used to
ob
tai
.n the maximum benefit from the Amp
fier.
Manual
assume using the Keithley Model 1081
10s
PULSE
AMPLIi=,ER
I :IGLlRE 1. Keithley Instruments
t lode1 108 Wideband Amplifier.
0465R
i”‘Lb”KL L. nelr”Ley ~“strumenrs
Model 109 Pulse Amplifier.
1
GENERAL DESCRIPTION
MODELS 108, 109 AMPLIFIERS
1-3.
Frequencyl:
Rise Time* (10% to 90%)
Overshoot3
Pulse Width for 10% Droop:
Input Impedance:
Voltage Gain (into 50-ohm
characteristic impedance)
Maximum rms Noise4:
Maximum Output (into 50-ohm
characteristic impedance)
Maximum Overload:
SPECIFICATIONS.
-3db
?0.5db
Model 108 (when powered by
the Model 1081 Power Supply)
1 kc and 180 MC
2.5 kc to 150 MC
Less than 3 nanoseconds
-
-
50 ohms
10 (20 db)
?2% at 10 kc
30 microvolts (7 db)
1.4 volts peak-to-peak
20 volts peak5
ac,
2.5 volts
dc,
Model 109 (when powered by
the Model 1081 Power Supply)
Less than 3 nanoseconds
Less than 2%
30 microseconds
50 ohms
10 (20 db)
i-2% at 10 kc
30 microvolts (7 db)
1.4 volts peak-to-peak
20 volts peak5
ac,
2.5 volts
dc ,
Overload Recovery6
Delay Time'
Change in Output Amplitude
for a 10% Line Voltage Change
(when powered by Model 1081):
1) db variations add when amplifiers are cascaded.
Maximum rise time for 3 amplifiers in cascade is less than 4 nanoseconds.
2)
3) Overshoot for amplifiers in cascade is 3% or less.
4) Noise referred to input measured from 10 cps to 100 MC. Noise of cascaded amplifiers is equal to noise of first amplifier only.
5) Continuous input power should not exceed l/8 watt.
6) Using a 100X overload test pulse 100 nanoseconds wide with 5-nanosecond fall
time to within 1% of base line.
or less overload shortens recovery time.
7) Delay times add when amplifiers are cascaded.
CONNECTORS: Input and Output:
POWER: +16 volts.dc and -12 volts dc; or 28 volts dc floating; ?5% accuracy; 50 milliam-
peres current (1.4 watts); +O.l% stability; Z-millivolt peak-to-peak maximum ripple; lOOmicrofarad filter from each power terminal to ground.
Less than 50 nanoseconds
Less than 5 nanoseconds
Less than 20.1%
A shorter pulse duration, a slower fall time
n type.
Power:
Amphenol 126-214
Less than 50 nanoseconds
Less than 5 nanoseconds
Less than *O.l%
DIMENSIONS, WEIGHT:
ACCESSORIES SIIPPLIED:
2
3 inches high x 2-l/4 inches wide x 3-3/4 inches deep; net weight, 12 oi
Mating power connector; mating input and output connectors.
0565R
MODELS 108, 109 AMPLIFIERS
1-4. APPLICATIONS.
The Model 108 Wideband Amplifier is used as a general Laboratory pre-amplifier in
a.
audio, radar, IF, TV and VHF work.
low noise permits amplification of signals in the microvolt region at low and high Irequev
ties. Because of its small size,
b. The Model 109 Pulse Amplifier is designed co amplify non-sinusoidal wave corms :.:ith
a fast rise time,
with oscilloscopes, high-speed counters,
L-5. ACCESSORIES. Refer to Section 6 for complete descriptions of the following Ampli-
fier accessories.
minimum overshoot and minimum ringing.
It can be used with all types of oscilloscopes. 11s
it can be designed into other equipment.
Common applications include use
pulse-height analyzers and phoro multipliers.
GmERAL DESCRIP~l'IO!;
Model 1081 Power Supply can power one,
a.
The POWer Supply operates from 105-125 or 210-250 Volt, 50-400 cps line sources; pocrr
rating is 12 watts. Its dimensions are the same as the hmplifi.ers; net weight is l-l,'?
pounds.
b. Model 1042 Accessory Kit provides useful adapters,
the Amplifier. The Kit accessories,
tion 6.
Model 1082 Mounting Plate adapts the Amplifiers and the Hodel LO81 for mounting LO
c.
another surface.
d. Model 1083 Cable allows using the filodels 108 and 109 with the Keicbley l$z,dcA1s lO(, ilnd
107 Amplifiers.
contained in a convenient case,
two or three Model 108 or 109 Amplifiers.
terminations and tee for use with
art‘ described in Scc-
FIGURE 3.
will power 1, ?
02h6R 3
>lodrl 1081 Power Supply Used twiti> 'Three Elodel 109 I'ulsc Amplifiers.
or 3 Amplifiers.
See Scdtior 6 ior the Power Supply description.
Tltc suppl)
GENERAL DESCRIPTION
MODELS 108, 109 AMPLIFIERS
1-6.
EQUIPMENT SHIPPED. The Models 108 and 109 are factory-calibrated and are shipped
with all components in place.
contains the Instruction Manual,
plugs.
All units are shipped for bench use. The shipping carton
a mating power connector and mating input and output
0266
MODELS 108, 109 AMPLIFIERS
OPERATIOX
SECTION 2. OPERATION
2-1.
cles are n-type. Input impedance is 50 ohms.
TERMINALS.
INPUT and OUTPUT Receptacles. INPUT (front panel) and OUTPlJ'~ (rear panel) Recepr;i-
a.
N-type connectros are used for their bccter
impedance characteristics and less leakage at higher frequencies than other popular connectors.
POWER Socket. The POWER Socket is a 4-pin connector.
b.
power cable supplied with the Model 1081 Power Supply.
It is compatible with the
Schematic Diagram 1797LD shows
the pin connections and voltages (refer to 5103).
2-2.
OPERATING PROCEDURES.
a. No control settings or preliminary adjustments are needed to operate either Ampli-
fier.
Both can be used immediately after they are connected to the ~lodel 1081 Power Suppl)
NOTE
The Amplifiers have n-type receptacles (Mil. No. 680/U). The Model 1042
Accessory Kit contains adapters to connect other type plugs to the Amplifier.
Section 6 describes the Kit.
Connect the Power Supply and associated equipment, such as an oscilloscope, on the
b.
same power line to avoid ac ground Loops.
may tend to be modulated by the ground Loops.
Otherwise,
the output signal from the Amplifi~cr
To further minimize ground loops, it may be
necessary to use isolation plugs on power line plugs of the Power Supply and the associa-
ted equipment. If a power supply other than the Model LO81 is used, put 100-,lf filter
capacitors from + and - to ground.
Use coaxial cables for connections,
c.
especially if working above 1 MC. Up to six
feet of coaxial cable may be used on the
Amplifier input and up to 12 feet on the out-
put,
50 ohms.
if the output cable is terminated with
Longer cables may be used, but the
Amplifier may not meet the flatness or over-
shoot specifications.
All cables used must
have a 50-ohm characteristic impedance.
NOTE
The Model LO9 has no phase reversal
on pulse.
at the input,
output,
input,
^ _
2-3.
a.
CASCfi"ING.
Up to four AmpliTiers may be cascaded
If the pulse is positive
it is positive at the
If it is negative at the
it is negative at the output.
0'6611
Keithley
Input: - AMI'LI- -Output:
6 feet
max.
source A
FIGURE 4.
FIER
Amplifier Cable Connections.
12 feet
max.
- 50-r:
Load
Maximum recommended cable length to input
is six feet; from output, 12 feet. If
longer cables arc used, the specified
ness
or overshoot may not be achieved. USC
flnt-
only coaxial cables.
3
OPERATION
MODELS 108, 109 AMPLIFIERS
together for gains of 100, 1000, or 10,000.
1.4 volts peak-to-peak into a 50-ohm load.
plifier stages and distortions will result.
gain hookups to reduce the noise level.
When using the 108 or 109 with the 106 or 107,
into the 106 and 107 power outlet.
Use the n-type male-to-male adapter from the Model 1042 Kit to cascade Amplifiers
b.
directly to each other. The Model 108 may also be used in cascade with the Keithley
Models 104 and 106 Amplifiers.
105 and 107 Amplifiers.
2-4. GAINS OTHER THAN 10, 100, 1000 AND 10,000.
"se attenuator pads in series with the Amplifier.
the attenuator pad on the last Amplifier OUTPUT Receptacle for input signals below 15
millivolts peak-to-peak for the best signal-to-noise ratio.
rms input signal is amplified 20 times (26 db)
Amplifier output.
the last output is 3 millivolts rms.
14-db pad, its level is 0.6 millivolt rms.
If the 14-db attenuator pad were used at the first Amplifier input, the output noise would
be 3 millivolts rms.
worse than previously.
Maximum input noise of each amplifier is 30 microvolts rms.
Signal-to-noise ratio would be approximately 6:1, or four times
The Model 109 may also be used in cascade with the Models
When the noise is attenuated five times through the
The final Amplifier output should not exceed
Higher outputs exceed the limits of the am-
A bandpass filter is recommended for lO,OOO-
NOTE
"se the 1083 cable for connection
For gains in between the cascaded values,
When two Amplifiers are cascaded, use
For example, a l-millivolt
using a 14-db attenuator pad on the last
Noise at
Signal-to-noise ratio is approximately 28:l.
2-5. OPEN CIRCUIT OPERATION.
gain changes for an open circuit.
megacycles, increasing as the frequency increases.
gain into an open circuit is approximately 10.5 to 11.
increases to approximately 18 (25 db) at 150 megacycles. The Amplifier will not oscillate
into an open circuit at any frequency, although standing waves become apparent at the
higher frequencies. The magnitude of the waves depends directly on cable length and
frequency.
2-6. AMPLIFIER NOISE. The main sources of noise are the transistors and any power supply
ripple. Since all noise is referred to the
input,
fier input noise times the amplifier gain (10).
The noise is measured at the output and referred back to the input. When two Amplifiers are cascaded,
amplifier is not significant because noise adds
as the square root of the sum of the squares.
2-7.
a. The rise time is defined as the time
needed for a signal to rise from 10% to 90%
of its final value.
amplifiers,
for the amplifier to go from 10% to 90%
of the final value of the input signal
the output noise will be the ampli-
the noise of the second
RISE TIME.
Specifically, for
rise time is the time needed
The specified Amplifier gain is into a 50-ohm load.
Output impedance is approximately five ohms below 10
Below 10 megacycles, therefore, the
Above 10 megacycles, the gain
IO%
G; /
28%
9
: ~-1
lli
FIGURE 5.
The gain linearity falls within the limits
shown above from 2.5 kc to 150 Mc.
GAlY LIWEI~II" _ YlllMUY GAIN mo* OK! IHL
I
I
1ow 1oow. I"/ 1011 10011 I", ,ou ,ool ,6,
Models 108 and 109 Gain Linearity
DlwM RAW 01 IM LYPllllER
1
1 I
I"IPUtK"
1 I
I
I
I
The
6
0266R
MODELS 108. 109 AMF'LIFIERS
OPCRATION
times the amplifier gain.
faster than the amplifier's, When amplifiers are cascaded,
Rise time is measured only with a pulse whose rise time is
the rise times add in qundra-
ture (square root of the sum of the squares).
The slight overshoot of a very high frequency pulse can be eliminated in Lhf >lodcl
b.
108 by detuning the high-frequency response slightly.
gain flatness for a continuous signal.
The Model 109 is already tuned lor
The Model 108 is tuned for msximum
minimum
ovcr-
shoot.
2-8. DELAY 'TIME.
Delay time is the transit time taken by a signal to go from the amplifier input to output. Because delay times are a physical constant, they add for cascaded
amplifiers.
2-9.
loops.
GROUND LOOPS.
This is a current - line or other frequency - flowing in a ground lead impedance
A common source of errors when amplifying Low-lcvcl signals is ground
which results in a voltage in addition to the desired signal voltage appearing ac tllc
input terminals of the amplifier.
Although the origin and mechanism of ground loops nrc
difficult to explain and trace, their effects can be reduced in several ways.
Make all ground lead impedances as low as possible.
a.
Employ only coaxial hookups wherever possible.
b.
Z-10.
STRAY FIELDS.
Stray fields can induce unwanted emf's in the test system.
'The in-
accuracies due to these fields become more significant as measurements become more scan-
sitivc. Induced emf's may be reduced by using coaxial cable having
minimum
loop area and
by using cables of minimum length.
0266R
7
MODELS 108, 109 AMPLIFIERS
CIKCUIT DESCRIPTION
SECTION 3.
3-1.
back.
epitaxial mesa transistors with a. l-gigacycle ft.
mizes lead inductance. Silver plating on the chassis eliminates ground loops and reduces
resistance due to skin effect at high frequencies.
ically sealed tantalum capacitors and metal film resistors insures excellent stabilit)
and long. trouble-free operation.
3-2. AMPLIFIER DESIGN.
es three high-frequency transistors, two in
cormnon emitter cascade configuration and
the third being an emitter follower for the
output. A high negative feedback loop is
used for gain stability.
GENERAL.
Both Amplifiers are of conventional RC-coupled cascade design, using negative fccd-
a.
There is no inductive peaking.
Careful circuit design allows for maximum performance. Point-to-point wiring mini-
b.
Refer to Schematic Diagram 1797LD at the back of the Manual for circuit
designations.
Each Amplifier us-
CIRCUIT DESCRIPTION
The wide bandwidth is achieved by using selected
Using solid-state components, hermet-
NOTE
The input is shunted by a 50-ohm me-
tay'film resistor (RlOZ), compensated for
a nominal 50-ohm input impedance across the
band.
sistor QlOl.
plify the signal and apply it to the emitter
f"ll"Wer, transistor Q103, which provides
low output impedance and higher power capabilities than the amplifier stages.
b.
fier stages is through resistor Rll6 and
capacitor CllO. The output of transistor
9102 is divided by resistor Rll6 and the
network, resistors R109, RllO and Rlll.
Potentiometer Rlll adjusts the gain at the
lower frequencies. Trirmners C103, C112,
Cl15 and Cl18 adjust the feedback at higher
frequencies, since the divider becomes pri-
marily capacitive.
stage, transistor QlOl, consists of two resistors, R105 and R106. Capacitor Cl05 is at
the midpoint between the two 2,2-kilobm resistors to eliminate ac feedback. Resistors
R114 and R115 and capacitor Cl08 provide the same function for transistor Ql02.
The input signal is applied to tran-
Transistors QlOl and 4102 am-
The feedback loop for the two ampli-
Each stage uses dc feedback from collector to base. The feedback loop for the first
c.
gram shows the stage design used in the 2-
stage amplifier.
the collector bias
bias voltage divider, which stabilizes the
base voltage. Resistor Rl supplies dc feedback. To eliminate degeneration caused by
the ac feedback, Rl is divided into two
parts, Rla and Rl
ses the ac from tie midpoint to ground.
Resistors Rl and R2 and
voltage drop provide a
Capacitor Cbp bypas-
.
P
0465R
9