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Back to : 108(108_252C109Amplifiers | HomeMODELS 108, 109 AMPLIFIERS CONTEXTS TABLE OF CONTENTSSection Page Section Page1. GENERAL DESCRIPTION . . . . . . . . 1 5-3. Models 108, 109 Lo\<-Frequency Calibration . . . 14 l-l. General . . . . . . . . 1 5-4. Model 108 High-Frcqurnc) 1-2. Models 108, 109 Differences . 1 Calibration . . . 14 l-3. Specifications. . . . . . . . 2 5-5. Model 109 High-Frequency 1-4. Applications. . . , . . .3 Calibration . . . 15 l-5. Accessories . . . . . . .3 5-6. Low-Frequency Response l-6. Equipment Shipped . . . . .3 Check........... 162. OPERATION . . . . . . . . .5 6. ACCESSORIES. . . . 19 2-1. Terminals . . . . . . . . . 5 6-l. Model 1081 Power Supply 19 2-2. Operating Procedures. . . . . 5 6-2. Model 1042 Accessory Kit . . 19 2-3. Cascading . . . . . . . . . . 5 6-3. Model 1082 Mounting Plate . 20 2-4. Gains Other Than 10, 100 1000 and 10,000. . . . . . . 6 7. REPLACEABLE PARTS. . . . . . . . . 21 2-5. Open Circuit Operation. . . . 6 2-6. Amplifier Noise . . . . . . . 6 7-l. Replaceable Parts List . . . 23 2-7. Rise Time . . . . . . . . . . 6 7-2. How to Order Parts . . . . . 23 2-8. Delay Time. . . . . . . . . . 6 Models 108, 109 Replaceable 2-9. Ground Loops. . . , . . . . 7 Parts List. . . . . . . . . 24 Z-10. Stray Fields. . . . . . . . 7 Model 1081 Replaceable Parts List. . . . . . . . . . . . 263. CIRCUIT DESCRIPTION ....... . 9 Models 108, 109 Schematic Diagram 17971D. . . . . . . 29 3-1. General .......... . 9 Model 1081 Schematic Diagram 3-2. Amplifier Design. ..... . 9 17966C. . . . . . . . . . 304. SERVICING ............ . 11 + Change Notice Last Page 4-1. General .......... . 11 4-2. Servicing Schedule. .... . 11 4-3. Parts Replacement ..... . 11 4-4. Troubleshooting ...... . 11 3~ Yellow Change Notice sheet is5. CALIBRATION ........... . 13 included only for instrument modifications affecting the 5-l. General .......... . 13 Instruction Manual. 5-2. Calibration Schedule. ... . 140266RMODELS 108, 109 AMPLIFIERS GENERAL DESCRIP'IIOS SECTION 1. GENERAL DESCRIPTIONl-l. GENERAL. The Keithley Models 108 and 109 are small, 12-ounce Xl0 gain amplifiers.The Model 108 is tuned for a wideband frequency response; the Model 109 is tuned ior pulseresponse. (See Figures 9 and 10 for illustrations of the two responses.) Both ?lodels re-quire an external power supply, preferably the Keithley Model 1081 Power Supply, whichcan drive up to three of these units at one time. a. The Model 108 bandwidth is from 1 kc to 180 MC (-3db). Response Erom 2.5 kc to150 MC is flat 20.5 db. Voltage gain is 10 (20 db) when terminated into a 50-ohm load.Up to four Model 108 Amplifiers may be cascaded for gains to 10,000, or one may be usedwith 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. b. The Model 109 Pulse Amplifier has a rise time of less than 3 nanoseconds (10:: to90%). Overshoot is less than 2%, pulse width for a 10% droop is 30 microseconds. Otherspecifications are the same as for the Model 108. Four Pulse Amplifiers may be cascadedfor gains to 10,000, or one may be used with other amplifiers to increase total gain by 10.l-2. MODELS 108, 109 DIFFERENCES. a. The Models 108 and 109 differ only in their tuning. The circuits and the parts areidentical. Most of the Instruction Manual applies to both units. Where there are differ-ences - such as application suggestions and calibration - the models are identified. b. Specifications and operations in this Manual assume using the Keithley Model 1081PO`Wer Supply to power the Amplifier. It is recommended that this Power Supblv be used toob tai .n the maximum benefit from the Amp fier. PULSE 10s AMPLIi=,ER I:IGLlRE 1. Keithley Instruments i"`Lb"KL L. nelr"Ley ~"strumenrs tlode1 108 Wideband Amplifier. Model 109 Pulse Amplifier.0465R 1GENERAL DESCRIPTION MODELS 108, 109 AMPLIFIERS1-3. SPECIFICATIONS. Model 108 (when powered by Model 109 (when powered by the Model 1081 Power Supply) the Model 1081 Power Supply)Frequencyl: -3db 1 kc and 180 MC ?0.5db 2.5 kc to 150 MCRise Time* (10% to 90%) Less than 3 nanoseconds Less than 3 nanosecondsOvershoot3 - Less than 2%Pulse Width for 10% Droop: - 30 microsecondsInput Impedance: 50 ohms 50 ohmsVoltage Gain (into 50-ohm 10 (20 db) 10 (20 db)characteristic impedance) ?2% at 10 kc i-2% at 10 kcMaximum rms Noise4: 30 microvolts (7 db) 30 microvolts (7 db)Maximum Output (into 50-ohm 1.4 volts peak-to-peak 1.4 volts peak-to-peakcharacteristic impedance)Maximum Overload: ac, 20 volts peak5 ac, 20 volts peak5 dc, 2.5 volts dc , 2.5 voltsOverload Recovery6 Less than 50 nanoseconds Less than 50 nanosecondsDelay Time' Less than 5 nanoseconds Less than 5 nanosecondsChange in Output Amplitudefor a 10% Line Voltage Change(when powered by Model 1081): Less than 20.1% Less than *O.l% 1) db variations add when amplifiers are cascaded. 2) Maximum rise time for 3 amplifiers in cascade is less than 4 nanoseconds. 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 am- plifiers 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. A shorter pulse duration, a slower fall time or less overload shortens recovery time. 7) Delay times add when amplifiers are cascaded.CONNECTORS: Input and Output: n type. Power: Amphenol 126-214POWER: +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; lOO-microfarad filter from each power terminal to ground.DIMENSIONS, WEIGHT: 3 inches high x 2-l/4 inches wide x 3-3/4 inches deep; net weight, 12 oiACCESSORIES SIIPPLIED: Mating power connector; mating input and output connectors.2 0565RMODELS 108, 109 AMPLIFIERS GmERAL DESCRIP~l'IO!;1-4. APPLICATIONS. a. The Model 108 Wideband Amplifier is used as a general Laboratory pre-amplifier inaudio, radar, IF, TV and VHF work. It can be used with all types of oscilloscopes. 11slow noise permits amplification of signals in the microvolt region at low and high Irequevties. Because of its small size, it can be designed into other equipment. b. The Model 109 Pulse Amplifier is designed co amplify non-sinusoidal wave corms :.:itha fast rise time, minimum overshoot and minimum ringing. Common applications include usewith oscilloscopes, high-speed counters, pulse-height analyzers and phoro multipliers.L-5. ACCESSORIES. Refer to Section 6 for complete descriptions of the following Ampli-fier accessories. a. Model 1081 Power Supply can power one, two or three Model 108 or 109 Amplifiers.The POWer Supply operates from 105-125 or 210-250 Volt, 50-400 cps line sources; pocrrrating 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, terminations and tee for use withthe Amplifier. The Kit accessories, contained in a convenient case, art` described in Scc-tion 6. c. Model 1082 Mounting Plate adapts the Amplifiers and the Hodel LO81 for mounting LOanother surface. d. Model 1083 Cable allows using the filodels 108 and 109 with the Keicbley l$z,dcA1s lO(, ilnd107 Amplifiers.FIGURE 3. >lodrl 1081 Power Supply Used twiti> 'Three Elodel 109 I'ulsc Amplifiers. Tltc suppl)will power 1, ? or 3 Amplifiers. See Scdtior 6 ior the Power Supply description.02h6R 3GENERAL DESCRIPTION MODELS 108, 109 AMPLIFIERS1-6. EQUIPMENT SHIPPED. The Models 108 and 109 are factory-calibrated and are shippedwith all components in place. All units are shipped for bench use. The shipping cartoncontains the Instruction Manual, a mating power connector and mating input and outputplugs. 0266MODELS 108, 109 AMPLIFIERS OPERATIOX SECTION 2. OPERATION 2-1. TERMINALS. a. INPUT and OUTPUT Receptacles. INPUT (front panel) and OUTPlJ'~ (rear panel) Recepr;i-cles are n-type. Input impedance is 50 ohms. N-type connectros are used for their bccterimpedance characteristics and less leakage at higher frequencies than other popular con-nectors. b. POWERSocket. The POWERSocket is a 4-pin connector. It is compatible with thepower cable supplied with the Model 1081 Power Supply. Schematic Diagram 1797LD showsthe 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. b. Connect the Power Supply and associated equipment, such as an oscilloscope, on thesame power line to avoid ac ground Loops. Otherwise, the output signal from the Amplifi~crmay tend to be modulated by the ground Loops. To further minimize ground loops, it may benecessary 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 filtercapacitors from + and - to ground. c. Use coaxial cables for connections,especially if working above 1 MC. Up to six Keithleyfeet of coaxial cable may be used on the Input: - AMI'LI- -Output:Amplifier input and up to 12 feet on the out- 6 feet FIER 12 feetput, if the output cable is terminated with max. max.50 ohms. Longer cables may be used, but theAmplifier may not meet the flatness or over-shoot specifications. All cables used musthave a 50-ohm characteristic impedance. - 50-r: NOTE source A Load The Model LO9 has no phase reversal on pulse. If the pulse is positive at the input, it is positive at the output, If it is negative at the FIGURE 4. Amplifier Cable Connections. input, it is negative at the output. Maximum recommended cable length to input is six feet; from output, 12 feet. If^ _2-3. CASCfi"ING. longer cables arc used, the specified flnt- ness or overshoot may not be achieved. USC a. Up to four AmpliTiers may be cascaded only coaxial cables.0'6611 3OPERATION MODELS 108, 109 AMPLIFIERStogether for gains of 100, 1000, or 10,000. The final Amplifier output should not exceed1.4 volts peak-to-peak into a 50-ohm load. Higher outputs exceed the limits of the am-plifier stages and distortions will result. A bandpass filter is recommended for lO,OOO-gain hookups to reduce the noise level. NOTE When using the 108 or 109 with the 106 or 107, "se the 1083 cable for connection into the 106 and 107 power outlet. b. Use the n-type male-to-male adapter from the Model 1042 Kit to cascade Amplifiersdirectly to each other. The Model 108 may also be used in cascade with the KeithleyModels 104 and 106 Amplifiers. The Model 109 may also be used in cascade with the Models105 and 107 Amplifiers.2-4. GAINS OTHER THAN 10, 100, 1000 AND 10,000. For gains in between the cascaded values,"se attenuator pads in series with the Amplifier. When two Amplifiers are cascaded, usethe attenuator pad on the last Amplifier OUTPUT Receptacle for input signals below 15millivolts peak-to-peak for the best signal-to-noise ratio. For example, a l-millivoltrms input signal is amplified 20 times (26 db) using a 14-db attenuator pad on the lastAmplifier output. Maximum input noise of each amplifier is 30 microvolts rms. Noise atthe last output is 3 millivolts rms. When the noise is attenuated five times through the14-db pad, its level is 0.6 millivolt rms. Signal-to-noise ratio is approximately 28:l.If the 14-db attenuator pad were used at the first Amplifier input, the output noise wouldbe 3 millivolts rms. Signal-to-noise ratio would be approximately 6:1, or four timesworse than previously.2-5. OPEN CIRCUIT OPERATION. The specified Amplifier gain is into a 50-ohm load. Thegain changes for an open circuit. Output impedance is approximately five ohms below 10megacycles, increasing as the frequency increases. Below 10 megacycles, therefore, thegain into an open circuit is approximately 10.5 to 11. Above 10 megacycles, the gainincreases to approximately 18 (25 db) at 150 megacycles. The Amplifier will not oscillateinto an open circuit at any frequency, although standing waves become apparent at thehigher frequencies. The magnitude of the waves depends directly on cable length andfrequency.2-6. AMPLIFIER NOISE. The main sources of noise are the transistors and any power supplyripple. Since all noise is referred to theinput, the output noise will be the ampli- IO% LIWEI~II" GAIN IHL GAlY _YlllMUY mo*OK! DlwM 01 LYPllllER RAW IMfier input noise times the amplifier gain (10).The noise is measured at the output and re-ferred back to the input. When two Ampli-fiers are cascaded, the noise of the second G; /amplifier is not significant because noise adds 28%as the square root of the sum of the squares. 9 : ~-12-7. RISE TIME. a. The rise time is defined as the time lli I1 I 1 1 I I I 1ow 1oow.I"/I I 101110011I", ,ou ,ool ,6,needed for a signal to rise from 10% to 90%of its final value. Specifically, for I"IPUtK"amplifiers, rise time is the time needed FIGURE 5. Models 108 and 109 Gain Linearityfor the amplifier to go from 10% to 90% The gain linearity falls within the limitsof the final value of the input signal shown above from 2.5 kc to 150 Mc.6 0266RMODELS 108. 109 AMF'LIFIERS OPCRATIONtimes the amplifier gain. Rise time is measured only with a pulse whose rise time isfaster than the amplifier's, When amplifiers are cascaded, the rise times add in qundra-ture (square root of the sum of the squares). b. The slight overshoot of a very high frequency pulse can be eliminated in Lhf >lodcl108 by detuning the high-frequency response slightly. The Model 108 is tuned for msximumgain flatness for a continuous signal. The Model 109 is already tuned lor minimum ovcr-shoot.2-8. DELAY 'TIME. Delay time is the transit time taken by a signal to go from the ampli-fier input to output. Because delay times are a physical constant, they add for cascadedamplifiers.2-9. GROUNDLOOPS. A common source of errors when amplifying Low-lcvcl signals is groundloops. This is a current - line or other frequency - flowing in a ground lead impedancewhich results in a voltage in addition to the desired signal voltage appearing ac tllcinput terminals of the amplifier. Although the origin and mechanism of ground loops nrcdifficult to explain and trace, their effects can be reduced in several ways. a. Make all ground lead impedances as low as possible. b. Employ only coaxial hookups wherever possible.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 andby using cables of minimum length.0266R 7MODELS 108, 109 AMPLIFIERS CIKCUIT DESCRIPTION SECTION 3. CIRCUIT DESCRIPTION3-1. GENERAL. a. Both Amplifiers are of conventional RC-coupled cascade design, using negative fccd-back. There is no inductive peaking. The wide bandwidth is achieved by using selectedepitaxial mesa transistors with a. l-gigacycle ft. b. Careful circuit design allows for maximum performance. Point-to-point wiring mini-mizes lead inductance. Silver plating on the chassis eliminates ground loops and reducesresistance due to skin effect at high frequencies. Using solid-state components, hermet-ically sealed tantalum capacitors and metal film resistors insures excellent stabilit)and long. trouble-free operation. NOTE Refer to Schematic Diagram 1797LD at the back of the Manual for circuit designations.3-2. AMPLIFIER DESIGN. Each Amplifier us-es three high-frequency transistors, two incormnon emitter cascade configuration andthe third being an emitter follower for theoutput. A high negative feedback loop isused for gain stability. The input is shunted by a 50-ohm me-tay'film resistor (RlOZ), compensated fora nominal 50-ohm input impedance across theband. The input signal is applied to tran-sistor QlOl. Transistors QlOl and 4102 am-plify the signal and apply it to the emitterf"ll"Wer, transistor Q103, which provideslow output impedance and higher power capa-bilities than the amplifier stages. b. The feedback loop for the two ampli- gram shows the stage design used in the 2-fier stages is through resistor Rll6 and stage amplifier. Resistors Rl and R2 andcapacitor CllO. The output of transistor the collector bias voltage drop provide a9102 is divided by resistor Rll6 and the bias voltage divider, which stabilizes thenetwork, resistors R109, RllO and Rlll. base voltage. Resistor Rl supplies dc feed-Potentiometer Rlll adjusts the gain at the back. To eliminate degeneration caused bylower frequencies. Trirmners C103, C112, the ac feedback, Rl is divided into twoCl15 and Cl18 adjust the feedback at higher parts, Rla and Rl . Capacitor Cbp bypas-frequencies, since the divider becomes pri- ses the ac from tie midpoint P to ground.marily capacitive. c. Each stage uses dc feedback from collector to base. The feedback loop for the firststage, transistor QlOl, consists of two resistors, R105 and R106. Capacitor Cl05 is atthe midpoint between the two 2,2-kilobm resistors to eliminate ac feedback. ResistorsR114 and R115 and capacitor Cl08 provide the same function for transistor Ql02.0465R 9MODELS 108, 109 AMPLIFIERS SECTION 4. SERVICING4-l. GENERAL. Section 4 contains the maintenance and troubleshooting procedures for theModels LO8 and 109. Follow these as closely as possible to maintain the instrument'sspecifications.4-2. SERVICING SCHEDULE. The Models 108 and 109 require no periodic maincennncc beyondthe normal care required of high-quality electronic equipment. Occasional C~CCKS 3s thefrequency or pulse response of the Amplifier should show the need for any ;ld~justocnL. SOpart should need frequent replacement under ordinary use.4-3. PARTS REPLACMENT. a. The Replaceable Parts List in Section 7 describes the electrical components of theAmplifiers. Replace components only as necessary. Use only reliable replacements whichmeet the specifications. Check the frequency or pulse response after any transiscar isreplaced. b. The transistors are selected for parameters which allow wide frequency response.Order these parts only from Keithley Instruments, Inc., or its representatives. NOTE Physical location of components greatly affects high frequency response. Put replaced parts and their leads in their exact previous position.4-4. TROUBLESHOOTING. a. The procedures which follow give instructions for repairing troubles which mightoccur in the ModeLs 108 and 109. Use the procedures outlined and use only speciiied re-placement parts. Make sure the external circuits are checked. Table 1 lists equipmentrecommended for troubleshooting. If the trouble cannot be located or repaired, contactthe nearest Keithley representative. Instrument Use Keithley Instruments Model 121 True RMS Measures ac voltages Voltmeter Keithley Model 153 DC Microvolt-Ammeter, Measure dc voltages 3% accuracy, 20 megohm input resistance Simpson Models 260 and 650 Transistor Check transistors Beta Testers Tektronix Type 504 Oscilloscope, passband Observe wave forms dc to 450 kc TABLE 1. Equipment Recommended for Troubleshooting. Use these instruments or their equivalents.0266R 11 SERVICING MODELS 108. 109 AMPLIFIERS Trouble Probable Cause Remedy Amplifier will not operate Faulty transistor Check QlOl, Ql02, Ql03; replace if faultv Noise with Amplifier Faulty transistor Check QlOl, QlO2, Q103; replace exceeds 30 microvolts rms if faulty Excessive ripple from Check power supply. Check power supply filters ClOl, C106, Cl16, C122, Cl23 and C124. Gain is more or less than 10 Potentiometer Rlll out Adjust Rlll per paragraph 5-3 of adjustment Model 108 frequency Amplifier out of cali- Calibrate per paragraph 5-4 response not flat within bration specifications Model 109 exceeds over- Amplifier out of cali- Calibrate per paragraph 5-5 shoot specification bration Rise time of Amplifier Amplifier out of cali- Adjust Model 108 per paragraph not within swcification I bration I 5-4. Model 109 oer oaraaarah 5-: Input impedance not Faulty R102 or Cl02 Check R102 and ClO2; replace 50 ohms I I if fault-v TABLE 2. Models 108 and 109 Troubleshooting. Refer to paragraph 4-4, b, before trouble- shooting the Amplifier. b. Before troubleshooting the Amplifier, check the external circuits, especially thepower supply. Make sure the Amplifier output is terminated into a good 50-ohm load. Checkthe coaxial cables and connections. Check the performance of the signal generator andother instruments. (The Amplifier will faithfully amplify any signal fed to it; a poor in-put results in a poor output.) Make sure the output signal does not exceed 1.4 volts peak-to-peak. If the external circuits are good, check the Amplifier itself. c. Table 2 contains troubles which might occurs with the instrument. If the repairsindicated in the table do not clear up the trouble, continue to search through a circuit-by-circuit check. Refer to the circuit description in Section 3 to find the more crucialcomponents and to determine their function in the circuit. The complete circuit schematicdiagram, 17971D, is in Section 7. d. If the instrument will not operate, check the power source. If it is satisfactory,continue to isolate the trouble. e. 'The Schematic Diagram indicates the transistor terminal voltages referenced to chas-sis ground. Measure the dc voltages to zlO% of indicated value with a dc voltmeter.12 0665RMODELS 108, 109 AMPLIFIERS CALIBRATIOII` SECTION 5. CALIBRATION5-l. GENERAL. a. The following procedures are recommended for calibrating and adjusting the >lodels108 and 109. Use the equipment recommended in Table 3. If propcr facilities arc notavailable or if difficulty is encountered, contact Keithley Instruments, inc., or itsrepresentative to arrange for factory calibration. b. Three calibrations are in the procedures: low-frequency calibration, higlr-frequen-cy wideband calibration and pulse calibration. In addition, paragraph 5-6 outlines testprocedures to check response. c. If the instrument is not within specifications after the calibration, follow thetroubleshooting procedures or contact Keithley Instruments, Inc., or its representative. Instrument Use General Radio GR-874 type attenuators, High frequency calibration 3 db, 6 db, 10 db and 20 db General Radio CR-874-WM50 50-ohm termin- Amplifier termination ation (also found in Keithley Instruments Model 1042 Accessory Kit) Hewlett-Packard Model 202A Audio Oscillator, Signal generator for low-frequency cali- 20 cps to 40 kc, 22% bration Jarrold Electronics Model 900-B Sweep Sig- Signal generator for Model 108 band nal Generator (includes Model D50 Detec- response to=), 500 kc to 1200 MC Keithley Instruments Model 121 True RMS Measure ac voltages Voltmeter Tee and adapters (found in Keithley Instru- Hook up calibration circuits ments Model 1042 Accessory Kit) Tektronix Type 111 Pulse Generator, 0.5-nsec Check Model 109 pulse response rise time, 2 to 20-nsec pulse duration Tektronix Type 504 Oscilloscope, passband Check wave form during tuning and view from dc to 450 kc sweep display of Model 108 Tektronix Type 561A Oscilloscope, with dual View Model 109 pulse response trace plug-in sampling units, 0.4-nsec rise time TABLE 3. Equipment Recommended for Models 108 and 109 Calibration. Use these instruments or their equivalents. 0565R 13CALIBRATION MODELS 108, 109 AMPLIFIERS5-2. CALIBRATION SCHEDULE. Check the Am-plifier response yearly or when transistorsare changed. Refer to paragraph 5-4 (Model108) or S-5 (Model 109) for procedures; re-calibrate completely if the response is not 5-4 (108) Icorrect. Always recalibrate the high-fre-quency gain if the low-frequency gain isadjusted.5-3. MODELS 108, 109 LOW-FREQUENCYCALI- I Low Frequency I Rlll 1 14 1 5-3 1BRATION TABLE 4. Models 108, 109 Internal Controls. The Table lists all internal controls, the a. Remove the Amplifier cower by remov- figure picturing the location, and theing the four screws. Connect the Amplifier paragraph describing the adjustment.to the Model 1081 Power Supply. b. Connect the Model 202A Oscillator to the Amplifier INPUT. Adjust the oscillator sig-nal for 50 millivolts rms at 10 kc. Connect the Model 121 Voltmeter, Type SO4 Oscillo-scope and 50-ohm termination to the Amplifier OUTPUT. The output signal should be 500millivolts rms *lo millivolts. Adjust potentiometer Rlll (Figure 14), if necessary, forthis output. c. Monitor the output signal on the oscilloscope and check for distortion. The low-frequency calibration establishes the base for the high-frequency re- SpO*Se. Therefore, tune the Amplifier at the high frequencies after tuning it at the low frequencies.5-4. MODEL 108 HIGH-FREQUENCY CALIBRATION. a. Remove the Amplifier by removing the four screws. Connect the Amplifier to the Model1081 Power Supply. Connect the Model 900-B Sweep Generator to the Amplifier INPUT direct-ly. See Figure 7. Connect the Amplifier OUTPUT to the Model D50 Detector. b. Adjust the generator signal to 50 millivolts rms and center the frequency at 100megacycles. Adjust the oscilloscope for a vertical display of 5%/cm.I Model 900-B Generator ver I ?IFIGURE 7. Block Diagram for Model 108 High-Frequency Calibration. Refer to Table 3 forequipment.14 0565RMODELS 108, 109 AMPLIFIERS CALIBRATION NOTE Use only an insulated alignment tool in adjusting the trimmers. DC biases are present across trimmer C118, and a screwdriver would short out the bia- ses and possibly damage transistor Q102. c. The low-frequency gain should be previously set (paragraph 5-3). Set trimmers C103,Cl12 and Cl15 (Figure 14) to their minimum values. Set trimmer Cl18 (Figure 12) to mini-mum by noting when the lowest high-frequency response curve appears on the oscilloscope.Set trimmer Cl15 to approximately l/3 of maximum to keep the Amplifier from oscillatin>:into an open circuit at higll frequencies. Set trimmer Cl03 near its maxiorunr. Set trimmerCl12 to approximately l/2 maximum. The response should rise at about 50 to 100 NC. d. Increase trimmer C118, watching the response curve on the oscilloscope. wl'hcn tileresponse looks like a straight line - either rising or descending - stop adjusting C118.Adjust trimmer Cl12 to bring the high end up or down to the proper gain level. If till?mid-range gain (between 50 and 100 MC) is not flat, alternate ad.justing trimmers CL03 andCl18 until the response is flat. If necessary, i-e-adjust trimmer Cl12 to bring the highend in perfectly. Response should be flat to at least 150 MC (refer to Figure 9). e. Insert a 3-db pad and re-adjust the oscilloscope for a vertical of X/cm. Check fora response of 5%. Using the oscilloscope vertical position control, put the display traceon a reference line. Remove the 3-db pad. The 180-megacycle point should bc above thepreviously set reference l.ine.5-5. MODEL 109 HIGII-FREQUENCY CALIBRATION, a. Remove the Amplifier cover by removing the four screws. Connect the Amplifier to theModel 1081 Power Supply. b. Connect the Type 111 Pulse Generator to the Sampling Oscilloscope. use attenuators(approximately 26 db) to adjust for a 0.7-volt peak pulse on the oscilloscope, Use thedelay cable on the pulse generator to adjust the pulse width to approximately 20 nanosec-onds. Set the oscilloscope horizontal sweep to 5 nanoseconds/cm and the vertical sensitiv-ity to 200 millivolcslcm. If necessary, use the pretriggcr output of chc pulse generatorto synchronize the oscilloscope. Note the amount of: overshoot and the shape on the pul-se's leading edge. The Amplifier is being calibrated at maximum output. Do not put in larger pulses than specified. This will cause overshooting and result in an impro- perly calibrated amplifier. c. Add a tee (included in the Model 1042 Kit) and 20.db attenuator; connect the pulsegenerator to the Amplifier INPUT. Set Figure 8. Connect the Amplifier OUTPUT Co theoscilloscope's other vertical input. Note the oscilloscope has 50-011111 input impedance,which terminates the Amplifier output. NOTE Use only an insulated alignment tool to adjust tile trimmers. DC biases are present across trimmer Cll8, nnd a screwdriver would short out tile hiascs anti possibly damage transistor Q102.06651~ 15CALIBRATION MODELS 108, 109 AMPLIFIERS Dual Channel Sampling Type 111 Oscilloscope Pulse Generator AMPLIFIER verFIGURE 8. Block Diagram for Model 109 High-Frequency Calibration. Refer to Table 3 forequipment. d. The low-frequency gain should be previously set (paragraph 5-3). Set trimmers ClO3,Cl12 and Cl15 (Figure 14) and Cl18 (Figure 12) to their minimum values. Set trimmer Cl15to approximately l/3 of its maximum value. Adjust trinuners Cl03 and Cl12 so that theoutput pulse looks exactly like the input pulse (Figure 11). If the input pulse has lessthan 1% overshoot and ringing, adjust trimmers Cl03 and Cl12 for less than 1% overshootand ringing on the output pulse. Keep trimmer Cl18 at its minimun value. e. Increase the oscilloscope sensitivity to 5 millivolts/cm and view the pulse tops.Slight adjustments of trimmer Cl15 may be necessary to make the output pulse exactly likethe input pulse, except for the rise time.5-6. LOW-FREQUENCY RESPONSECHECK. Connect the Model 202A Oscillator to the AmplifierINPUT. Adjust the oscillator signal to 50 millivolts rms at 10 kc. Use the Model 121Voltmeter to monitor the Amplifier output. Terminate the output into 50 ohms. The out-put voltage at 10 kc should be 500 millivolts rms ?2%. Gradually decrease the signalfrequency. The output amplitude should not vary more than 5% until 2.5 kc.16 0565RMODELS 108, 109 AMPLIFIERS CALIBRATIONFIGURE 9. Models 108 and 109 Bandwidth FIGURE 10. Models 108 and 109 OvershootCharacteristics. The Model 108 is widk- Characteristics. The Model 108 is wide-band tuned; the Model 109, pulse tuned. band tuned; the Model 109, pulsf tuned.The response is from 0 cps (extreme left) The oscilloscope is set far 5 nscc/cmto 240 MC; each pip represents 10 MC. horizontal, 0.2 v/cm vertical. The pulseDisplay signal of 50 mv rms is from a amplifier has minimum pulse distortion atsweep generator. The excellent flatness the expense of flatness (see Figure 9).of the wideband amplifier is gained at theexpense of overshoot and ringing on pulses. FIGURE 11. Pulse Fidelity of Model 109 Pulse Amplifier. Note bow the output pulse follows the input pulse.0665R 17CALIBRATION MODELS 108, 109 AMPLIFIERSFIGURE 12. capacitor Locations. The INPUT FIGURE 13. Resistor Locations. The INPUTReceptacle is at the top of the illustra- Receptacle is at the top of the illustra-tion. Both the Models 108 and 109 have the tion. Both the Models 108 and 109 have thesame component locations. same component locations. FIGURE 14 (left). Component Locations, Reverse Side. The INPUT Receptacle is at the top of the illustration. Both the Models 108 and 109 have the same component locations.18 0665RMODELS 108, 109 AMPLIFIERS ACCESSORIES SECTION 6. ACCESSORIES6-1. MODEL 1081 POWERSUPPLY. a. GfZ"C2Xll. The Keithley Model 1081 Power Supply furnishes the power required for one,two or three Models 108 and 109 Amplifiers. No adjustment is necessary. Refer to Section7 for the Power Supply Replaceable Parts List and Schematic Diagram. b. Specifications. Output: As required for 1, 2 or 3 Models 108 and 109 Amplifiers. 28 volts dc float- ing; ?5% accuracy; 150 milliamperes current; fO.l% stability; 3-millivolt peak-to-peak maximum ripple. Power Required: 105-125 or 210-250 volts, 50-400 cps, 12 watts. Dimensions, Weight: 3 inches high x 2-l/4 inches wide x 3-3/4 inches deep; net weight, l-1/2 pounds. Accessories Supplied: Three Power Cables 3 feet long for connecting the Model 1081 to the Model 108 or 109 Amplifier. c. Operation. Use the Power Cable to con-nect the Power Supply to the Amplifier. One,two or three Amplifiers can be connected atone time. Connect the Model 1081 to the po-wer line. Snap the front panel slide switchon to turn the instrument on. No warm-up GIJW 15. Keithley Instruments Model 101time or adjustment is necessary. For 234- wer Supply.volt power sources, refer to Schematic Dia-gram 17966C for rewiring the transformer. d . Circuit. (Refer to Schematic Diagram 17966C.) The Model 1081 is relatively simplefor its specifications. Unregulated voltage from the transformer, Tl, is rectified bydiodes DI.01 to D104 and filtered by capacitor ClOl. The voltage is applied to transistorQl , connected as a series regulator. The output is sampled by resistors R106 and R108and compared to the voltage across zener reference diode D106. Any voltage difference isamplified by transistors Q2 and Q3, operating as a differential voltage amplifier, andapplied to the series regulator. The fuse is in series with the output. If the Power sup-ply is overloaded, the fuse will blow. Ordinarily, the fuse will not blow, even if Ampli-fiers arc connected or disconnected while the Power Supply is on.6-2. ?lODEL 1042 ACCESSORYKIT. The Model 1042 Accessory Kit provides useful adapters, n50-ohm termination and a tee for USC with the Amplifiers. The Kit cast is 2 inches highx 12 inches wide x 8 inches deep with polyethylene-foam compartments. It ireiglis npprosi-matcly tlircc pounds.0665R 19ACCESSORIES MODELS 108, 109 AMPLIFIERS6-3. MODEL 1082 MOUNTING PLATE. (Refer to Figure 16 for dimensions). a. The Model 1082 enables a Model 108, 109 or 1081 to be installed in a system. Itprovides a,mounting surface for 0. E. M. applications. b. To mount an instrument on the Plate, remove the four feet from the Amplifier orPower Supply. Attach the Plate to the instrument with the No. 4 flathead screws. Makesure the screw heads are flush with the Plate to avoid interference. The Plate and instru-ment may be mounted to another surface in any desired position. Item Keithley ?ig. 15 Description Part No. 1 50-ohm Termination, General Radio Type 874 cs-159 2 Adapter, male n to female uhf cs-114 3 Adapter, male n to female bnc CS-116 4 Adapter, male n to male n cs-158 5 Adapter, male n to General Radio Type 874 cs-109 6 Adapter, n-type tee cs-157 7 Adapter, male n to General Radio Type 874 cs- 109 8 Adapter, male n to male n CS-158 9 Adapter, male n to female bnc CS-116 10 Adapter, male n to female uhf cs-114 TABLE 5. Contents of Model 1042 Accessory Kit. FIGURE 15. plodcl 1042 Accessory Kit. See Table 5 for contents.20 0665RMODELS 108, 109 AMPLIFIERS ACCESSORIES FIGURE 16. Dimensions of the Model 1082 Mounting Plate.0266 21MODELS 108, 109 AMPLIFIERS REPLACWBLE PARTS SECTION 7. REPLACEABLE PARTS7-1. REPLACEABLE PARTS LIST. The Replaceable Parts List describes the components of theModels 108 and 109 Amplifiers and the Model 1081 Power Supply. Both Amplifiers "se thesame components. The List gives the circuit designation, the part description, a suggestedmanufacturer, the manufacturer's part number and the Keithley Part Number. 'Tllf last col-umn indicates the figure picturing the part. The name and address of the manufacturerslisted in the "Mfg. Code" column are in Table 7.7-2. HOWTO ORDER PARTS. a. For parts orders, include the instrument's model and serial number, the Kcithlc!Part Number, the circuit designation and a description of the part. All structural partsand those parts coded for Keithley manufacture (80164) must be ordered from KcithleyInstruments, Inc., or its representive. In ordering a part not listed in the ReplaceableParts List, completely describe the part, its function and its location. b. Order parts through your nearest Keithley representative or Sales Service Department,Keithley Instruments, 1~. M or meg mfga (106) or megohms m milli (10`3) CerT Ceramic, 'Tubular Mfg. Maanufacturcr CerTr Ceramic Trimmer Mil. No. Nilitary Type Number Comp Composition MtF Metal Film compv Composition Variable MY Mylar DCb Deposited Carbon ETB Electrolytic, Tubular P pica (10"') ETT Electrolytic, 'Tantalum Ref. Refcrcnce f farad Fig. Figure I! micro (10-6) FT Feed 'Through " volt k kilo (103) Var Variable w watt TABLE 6. Abbreviations and Symbols.0565RREPLACEABLE PARTS MODELS 108, 109 AMPLIFIERS MODELS 108, 109 REPLACEABLE PARTS LIST (Refer to Schematic Diagram 17971D for circuit designations.) CAPACITORSCircuit Mfg. Mfg. Keithley Fig.Desig. Value Rating TYPO Code Part No. Part No. Ref.Cl01 500 pf 500 " FT 71590 MFTSOO c15-5OOP 12Cl02 1.2 Qf 20 " ETT 05397 KlR2J20K C80-1.2M 12Cl03 4.5-25 pf 500 v CerTr 71590 822AZ C76-4.5/25P 14Cl04 1.2 pf 20 v ETT 05397 KlR2J2OK C80-1.2M 12Cl05 1.2 vf 20 " ETT 05397 KlRZJ20K CBO-1.2M 12Cl06 500 pf 500 v FT 71590 MFTSOO c15-SOOP 12Cl07 1.2 I.lf 20 v ETT 05397 KlR2J20K C80-1.2M 12Cl08 1.2 pf 20 v ETT 05397 KlR2J2OK CBO-1.2M 12Cl09 0.1 pf 50 v MY 84411 601PE C41-O.lM 12Cl10 1.2 uf 20 v ETT 05397 KlR2J2OK C80-1.2M 12Cl11 1.2 pf 20 v ETT 05397 KlR2J20K C80-1.2M 12Cl12 4.5-25 pf 500 v CerTr 71590 822AZ C76-4.5/25P 14Cl13 0.1 ,if 50 v MY 84411 6OlPE C41-O.lM 12Cl14 0.1 Llf 50 " MY 84411 6OlPE C41-O.lM 12Cl15 4.5-25 pf 500 v CerTr 71590 822AZ C76-4.5/25P 14Cl16 500 pf 500 " FT 71590 MFTSOO c15-SOOP 12Cl17 4.7 ,lf 20 " ETT 05397 K4R732OK C80-4.7M 12Cl18 1.5-3 pf 500 " CerTr 71590 822DZ C76-1.5/3P 12Cl19 10 pf 600 v CerT 71590 TCZ c77-1OP 12Cl20 10 pf 600 v CerT 71590 TCZ c77-1OPCl21 10 pf 600 v CerT 71590 TCZ c77-1OP 12Cl22 500 pf 500 v FT 71590 MFT500 c15-SOOP 12Cl23 500 pf 500 v FT 71590 MFT500 c15-SOOP 12Cl24 500 pf 500 v FT 71590 MFTSOO c15-SOOP 12 DIODESCircuit Mfg. Keithley Fig.Desig. TYPO Number Code Part No. Ref.DlOl Silicon lN3253 02735 RF-20 14D102 Silicon lN3253 02735 RF-20 14 CONNECTORSCircuit Mfg. Keithley Fig.Des&. Description Code Part No. Ref.JlOl Receptacle, n, INPUT, Mil. No. W-680/U (Mfg. No. 82-811) 02660 cs-955102 Receptacle, n, OUTPUT, Mil. No. UG-680/U (Mfg. No. 82-811) 02660 cs-95 24 0165 MODELS 108, 109 AMPLIFIERS RCPLACEABLI: PARTS CONNECTORS(Cont'd) Circuit Mfg. Keithlc) Fig. Desig. Description Code Part No. Ref. - (F)Plug, n, Mate of .I101 and 5102, Mil. No. UG-536/U (Mfg. No. 309-34000) 02660 E-96 JlO3 Receptacle, POWER . Locking Ring (Mfg. No. 126-1430) 02660 ~~-165 . Receptacle (Mfg. No. 126-1429) 02660 (X-163 Body (Mfg. No. 126-1425) 02660 CS-163 - (F)&ug, Mate of J103 (Mfg. No. 126-1427) 02660 CS-162 RESISTORSCircuit Mfg. Mfg. Kcithle) l:ig.Desig. Value Rating TYPO Code Part No. Part No. Ref.RlOl 47 kn lO%, l/4 w Comp 44655 RC07 R76-47K 13R102 50 i: l%, l/8 w MtF 07716 CL% 1~88-49.9 13R103 47 n lO%, l/4 w Comp 44655 RC07 R76-47 13R104 470 (1 lO%, l/4 w Comp 01121 CB R76-470 13R105 2.2 kr? lO%, l/4 w camp 44655 RC07 R76-2.2K 13R106 2.2 ki? lO%, l/4 w Comp 44655 RC07 R76-2.2K 13R107 47 i lO%, l/4 w camp 44655 RC07 R76-47 13R108 47 k!l lO%, l/4 w Comp 44655 RC07 R76-47K 1, 3R109 60.4 G l%, l/8 w MtF 07716 CL4 R88-60.4 13RllO 100 ? l%, l/8 w MtF 07716 CrA R88-100 13Rlll 1 k?