Tektronix 070-1616-00 User's Manual
Contents
1. the input is assumed the negative input Fig 1 4 Conventional Operational Amplifier symbols Understanding Operational Amplifiers Operational amplifiers are devices which make use of negative feedback to process signals with a high decree of accuracy in the ideal situation this accuracy is limited only by tolerances in the value of the passive elements in the input and feedback networks The operational amplifier is a high gain amplifier de signed to remain stable with large amounts of negative feedback from the output to the input 1 3 Operating Instructions AM 501 General purpose types with precise values of gain are used for linear amplification and for accurate integration or differentiation operations Negative feedback 2 Fig 1 48 from the output to the input of the amplifier is obtained by connecting the output to the minus input through a resistor capacitor or a non linear impedance device With negative feedback the operational amplifier oper ates like self batancing bridge It attempts to provide the current needed through the feedback network to maintain the minus input at a null or ground potential The output signal voltage then is a function of this feedback current and the impedance of the feedback element lf the amplifier minus input is held near ground potential by the feedback current it will appear as a low impedance point to any input signal With a res2. C too large or C too small n TARS Compensated Differentiator E mox limited to dEn C too large dE Fig 1 13 Compensated differentiator max limited to 2 i Operating Instructions AM 501 Transient Response Frequency Response integrator Direct compensation not recommended see fexi T error too large Citoo large Fig 1 14 integrator direct compensation not recommended current needed to establish the null at the start of the waveform without having to develop excess voltage across Ri This capacitance limits the output voltage maximum to approximately dEin Ci C2 After an abrupt change in the input waveform when dEin is small but dEin dt X RC is large the output voltage limitation of dEin Ci Cz may result in a significant error The solution in this case is to select a larger value of Ci and smaller values Rf and C2 keeping the Rt Ci time constant the same to reduce the error and keep its duration as short as possible integrator Compensation Compensation to integrate fast rise input signals is not recommended The added components introduce more stray capacitance 11 is recommended that smaller values of Ri and a larger Cr be used to maintain the same time constant This is limited by how much loading the signal source can tolerate when Ri is re
3. 2 5 by 2 X 105 X 1 X 10 yields 5 mV s Due to the polarity re versal in the amplifier it is necessary to multiply by RC to obtain the proper sign in the answer If the waveform contains both positive and negative polarities during the integrating period the output is proportional to the difference between the volt seconds of the two polarities because the integrator is an averaging device The two polarities may be added by preceding the integrator with an absolute value amplifier full wave rectifier to invert one of the two polarities Operational Amplifier Specifications and Limita tions The ideal operational amplifier would provide an infinite amount of gain infinite input impedance and zero output impedance With these ideal conditions the operational amplifier could process signals with an accuracy that is limited only by the tolerances in the values of the passive elements in the input and feedback network The practical amplifier has finite values for all three which determine the limits of accuracy in all applications Some of the pro minent limitations are 1 Open loop gain 2 Gain bandwidth product 3 Output current and voltage capabilities 4 Signal source impedance Open Loop Gain The accuracy of all operations is ultimately limited by the open loop gain of the amplifier which is a determinant of how close the amplifier holds the null at the minus input The ideal amplifier with infinite gain wo
4. 72982 72982 72982 72982 72982 72982 72982 72982 72982 80009 80009 80009 80009 07910 04713 04713 07910 80009 07910 80009 07910 07910 07910 07910 07910 71744 24931 58474 58474 24931 58474 58474 58474 24931 58474 80009 80009 80009 80009 07263 07263 07263 12040 15818 07263 12040 670 2958 00 39D757G040HI4 390757 040 24 30 106 1000 4 30D106F100DC4 831 516 102 831 516 102 301 000C0G0150G 301 000COGOlO0F 831 516 102 301 000 0 0100 301 0000230680 831 50025D471J 301 000 060100 301 0000220680 152 0488 00 152 0488 00 152 0107 00 152 0107 00 184152 IN5298 IN5298 iN4152 152 0061 00 1N4152 152 0061 00 184152 1N4152 1N4152 184152 1 4152 7220 2828200 1 BB10167G2BX BB10167G2BX 28JR200 1 DF2l1WTC DF21WTC BINP BB10167Gi3T 28JR200 1 BINP 10167613 151 0436 00 151 0436 00 151 0347 00 151 0347 00 525381 285401 525381 NS7410 502115 525381 NS7410 3 4 Electrical Parts List AM 501 Tektronix Serial Model Mir No No Dscont Name amp Description l Code Mfr Part Number Q135 151 0228 00 TRANSISTOR SILICON PNP SEL FROM 2N4888 07263 521862 0140 151 0228 00 TRANSISTOR SILICON PNP SEL FROM 2N4888 07263 821862 Q145 151 0279 00 TRANSISTOR SILICON NPN 07263 525381 0150 8 151 0232 00 TRANSISTOR SILICON NPN DUAL 12040 57348 9165 151 0350 00 TRANSISTO
5. equal to 1 volt per second This rate of rise continues until the input voltage is changed or the amplifier reaches its swing limit if the input signal to Zi is removed before the amplifier reaches its output limit the output voltage remains at the level reached when the signal was removed The 14A current through Zt to balance or the input is no longer required therefore under ideal conditions the output voltage remains at this level indefinitely or until an input signal is again applied to Zi Absolute integrator output level at the end of some interval of time is the sum of the products of each voltage applied to Zi times the period of each applied voltage divided by The mathematical expression of the output level in a given period from t to ty is 1 dt ac la Em Eout The integral sign f indicates the summation of all the products Ein X dt shown between the time limits of t and t5 The expression dt represents infinitesimal incre ments of time integrator Understanding manipulations in integral calculus is not necessary to operate an operational amplifier as an inte grator The operational amplifier used as an integrator provides a voltage output that is proportional to the net number of volt seconds applied to the input if the total volt seconds of one polarity is equalled by volt seconds of the opposite polarity the output level at the end of the selected interval is zer
6. gain linear amplifier Gain is Fig 1 5 Operational Amplifier with resistors for both 2 and 24 Differentiation If Zi is replaced with a capacitor Fig 1 6 the following action occurs Since apparent current through a capacitor is tional to the rate of change of the voltage across the capacitor steady state DC voltage across the capacitor assuming an ideal capacitor will produce no current through the capacitor Therefore with a steady DC voltage applied to an input capacitor there is no requirement for balancing current from Zt to maintain the ground potential at the minus input to the operational amplifier Output voltage therefore will be zero With a change of the voltage at the input there will be a proportional apparent current flow through the input capacitor The amount of this current flow is dependent on the voltage rate of change and the amount of input cap acitance i e C de dt To illustrate assume the poten tial at the input starts at 100 volts DC and is changed at a linear rate to 95 volts in 5 seconds This is a rate of change of 1 volt per second 5 V 5s 1 V s If the value of Zi is 1 uF constant 1 flows through Zi during the 5 second period 1 C de dt The amplifier generates an equal and opposite current through Zt to balance the circuit If Zt is a 1 MQ resistor the 14A current will generate 1 volt at the amplifier output The output therefore s
7. on As the current increases 020 will finally turn Q10 off thus limiting the current CR60 serves as a protective diode preventing the positive power bus from going below ground 49 V supply operates nearly the same as the 49 V supply 25 V AC is bridge rectified by CR12 and added to 33 5 V DC from the power module VR52 references the negative input of U20 an operational amplifier The 49 V is adjusted by R12 connected to the plus input of U20 Hf the load on the 49 V supply increases the voltage will go more positive This causes pin 3 of U20 to move in the positive direction through R32 and R12 Pin 6 of U20 goes positive increasing conduction in Q12 restoring the 49 V and causing equilibrium at pins 2 and 3 of 020 the load on the 49 V supply increases to the point of causing the voltage drop across R52 to turn O22 on pin 3 of U20 wil go negative causing the base of 12 to go negative This reduces the current to the load to within safe limits Section 3 501 REPLACEABLE ELECTRICAL PARTS PARTS ORDERING INFORMATION Replacement parts are availabie from or through your local Tektronix Inc Field Office or representative Changes to Tektronix instruments are sometimes made to accommodate improved components as they become available and to give you the benefit of the latest circuit improvements developed in our engineering department It is therefore important when ordering parts to include
8. 0 Operating Instructions AM 501 Fig 1 10 Shunt Impedance across input Where 2 is large com pared to 2 and Zi and open loop gain A is high effect of Z is negligible The general expression for the closed loop gain dis cussed later in this text of an operational amplifier Eout 24 may be modified Ein Zi Zt Nee to show the effect of shunt impedance Zs across the minus input keeping in mind that A is a negative number As it becomes smaller the effect of Zs on accuracy becomes apparent and may become comparable to that of Z Zi The terms in the above equation can be rearranged to show the effect of Zs as related to Zi Eout 7 24 Ein Zi 1 et 2 i Zs Closed Loop Gain Accuracy For Amplification Common usage in the analog computer field assigns a negative number to the open loop gain between the minus input and the output and a positive number to the gain from the plus input Therefore in calculating values from formulas invoiving A and the minus input it is necessary to keep in mind that A 5 a negative number and the expression 1 A when A is 10 000 equals 10 001 not 9999 One simplification has been made Closed loop gain commonly expressed as Zs Zi 1 24 has been reduced to PE Z 24 1 it may also be written Zt 1 i 1 1 Z Zi A This more clearly shows the effect of A on accuracy Gain Band
9. 01121 GB1225 R100 321 0168 00 RES PXD FILM 549 OHM 12 0 125W 75042 CEATO 5490F 2101 321 0212 00 RES PXD FILM 1 58K 1 0 125 75042 CEATO 1581F R102 323 0352 00 RES FXD FILM 45 3K OHM 1 0 50W 75042 4532 R105 321 0202 0900 RES FXD FILM 1 24K OHM 1 0 125W 75042 CEATO 1241F 2115 321 0164 00 RES FXD FILM 499 0HM 1 0 125W 75042 CEATO 4990F 2116 321 0164 00 RES FXD FILM 499 1 0 125 75042 CEATO 4990F R119 316 0102 00 RES FXD COMP 1K OHM 10 0 25W 01121 1021 R120 321 0289 00 RES FXD FILM 10K OHM 1 0 125W 75042 CEATO 1002F 5122 311 0607 00 RES VAR NONWIR 10K OHM 10 0 50W 80740 6259 3 R124 321 0289 00 RES FXD FILM 10K 18 0 1254 75042 CEATO 1002F R125 321 0202 00 RES FXD FILM 1 24K OHM 1 0 125W 75042 1241 R126 321 0212 00 RES FXD FILM 1 58K 18 0 125 75042 CEATO 1581F R130 321 0164 00 RES FXD FILM 499 OHM 1 0 125W 75042 CEATO 4990F 8132 321 0164 00 RES FXD FILM 499 0HM 1 0 125W 75042 CEATO 4990F R150 321 0164 00 RES FXD FILM 499 0HM 1 0 125W 75042 0 4990 8152 321 0164 00 RES FXD FILM 499 OHM 1 amp 0 125W 75042 CEATO 4990F R165 315 0302 00 RES FXD COMP 3K OHM 5 0 25W 01121 3025 R167 315 0242 00 RES FXD COMP 2 4K 0HM 5 0 25W 01121 2425 2168 315 0510 00 RES PXD COMP 51 OHM 5 0 25W 01121 5105 R170 315 0913 00 RES FXD COMP 91K OHM 5 0 25W 01122 9135 R171 316 0183 00 RES FXD COMP 18K OHM 10 0 25W 01121 1831 8172 3
10. 0PF 1PF 500V DI 68PF 10 500V DI 470PF 5 500V DI 10PF 1PF 500V DI 68PF 10 500V SEMICOND DEVICE SILICON 200V 1500MA SEMICOND DEVICE SILICON 200V 1500MA SEMICOND DEVICE SILICON 375V 400MA SEMICOND DEVICE SILICON 375V 400MA SEMICOND DEVICE SILICON 30V 150MA SEMICOND DEVICE 100V 1MA SEMICOND 100 1 SEMICOND DEVICE SILICON 30V 150MA SEMICOND DEVICE SILICON 175V 100MA SEMICOND DEVICE SILICON 30V 150MA SEMICOND DEVICE SILICON 175V 100MA SEMICOND DEVICE SILICON 30V 150MA SEMICOND DEVICE SILICON 30V 150MA SEMICOND DEVICE STLICON 30V 150MA SEMICOND DEVIC SILICON 30V 150MA SEMICOND DEVICE SILICON 30V 150MA LAMP INCAND 18V 26MA CONNECTOR RCPT BNC FEMALE POST BDG ELEC RED 5 WAY MINIATURE POST BDG ELEC RED 5 WAY MINIATURE CONNECTOR RCPT BNC FEMALE POST BDG ELEC WHITE 5 WAY MINIATURE POST BDG ELEC WHITE 5 WAY MINIATURE POST BDG ELEC CHARCOAL 5 WAY MINIATURE CONNECTOR RCPT BNC FEMALE POST BDG ELEC CHARCOAL 5 WAY MINIATURE TRANSISTOR SILICON NPN TRANSISTOR TRANSISTOR SILICON NPN TRANSISTOR TRANSISTOR TRANSISTOR TRANSISTOR TRANSISTOR SILICON PNP DUAL TRANSISTOR SILICON JFE DUAL TRANSISTOR TRANSISTOR SILICON PNP DUAL SILICON NPN SILICON NPN SILICON NPN SILICON PNP SILICON NPN SILICON NPN Electrical Parts List AM 501 Mfr Code Mfr Part Number 80009 56289 56289 56289 56289 72982
11. 16 0681 00 RES FXD COMP 680 10 0 25 01121 6811 R175 316 0220 00 RES FXD COMP 22 OHM 10 0 25W 01121 cB2201 R183 316 0331 00 RES FXD COMP 330 10 0 257 01121 cB3311 R185 316 0220 00 RES FXD COMP 22 OHM 10 0 25W 01121 CB2201 R186 316 0471 00 RES FXD COMP 470 OHM 10 0 25W 01121 CB4711 3 5 REV B SEP 1974 Tektronix Serial Model No No Part No Eff Dscont Name amp Description R190 315 0302 00 RES FXD COMP 3K OHM 5 0 25W 8192 315 0242 00 RES FXD COMP 2 4K OHM 5 0 25W R193 315 0510 00 5 51 5 0 25 8120 260 1206 00 SWITCH TOGGLE SPDT 5A 115VAC CENTER OFF 010 156 0067 00 MICROCIRCUIT LE OPERATIONAL AMPLIFIER u20 156 0067 00 MICROCIRCUIT LI OPERATIONAL AMPLIFIER VR20 152 0283 00 SEMICOND DEVICE ZENER 0 4W 43V 5 VR22 152 0255 00 010100 8029999 SEMICOND DEVICE ZENER O 4W 51V 5 VR22 152 0283 00 030000 SEMICOND DEVICE ZENER 0 4W 43V 5 VR50 152 0461 00 SEMICOND DEVICE ZENER 0 4W 6 2V 5 VR52 152 0461 00 SEMICOND 0 4 6 2 5 110 152 0175 00 SEMICOND DEVICE ZENER 0 4W 5 6V 5 VR126 152 0195 00 SEMICOND DEVICE ZENER 0 4W 5 1V 5 VR135 152 0195 00 SEMICOND DEVICE ZENER 0 4W 5 1V 58 VRi4O 152 0175 00 SEMICOND DEVICE ZENER O 4W 5 6V 5 REV B SEP 1974 Electrical Parts List AM 501 Mfr Code 01121 01121 01121 09353 80009 80009 04713 04713 04713 04713 04713 04713 81483 81483 04713 Mfr Part
12. 5 to turn on taking emitter current from the current source 0165 When the load current reaches its limit enough current is diverted from 0165 to shut 0170 off and prevent the output from moving any further positive 2 2 The same current limiting occurs in the other direction negative swing at the output R193 senses the load current CR190 turns on taking current from 0190 and preventing the negative driving signal from driving the output too far negative CR175 and CR185 prevent 0170 and 0180 from reaching base emitter reverse breakdown during conditions of output overload or short circuit CR175 and R186 prevent oscillation when the output is capacitively loaded Power Supply CR10 bridge rectifies 25 AC from the power module This voltage is added to the 33 5 V DC from the power module to provide raw DC for the regulated 49 V DC The 33 5 V is applied to pin 7 Vec of the operational amplifier U10 The plus input is referenced by VR50 The output voltage is sensed through R30 to the minus input of 1 VR20 allows 010 to operate near ground while controlling the current through Q10 R10 sets the output voltage If the output voltage decreases pin 2 of U10 goes negative causing pin 6 to do positive This action increases the current flow through O10 to the load bringing the voltage across the load to its original value If the current through Q10 becomes excessive the voltage dropped across R50 will turn 020
13. 7 CR140 CRl45 CR165 175 CR185 CR190 5580 2118 2119 2120 7123 1124 2125 2174 2175 1176 010 012 020 022 0100 0105 0110 Q115A B Q120A B Q125 Q130A B Tektronix Part No 670 2958 00 290 0324 00 290 0324 00 290 0194 00 290 0194 00 283 0000 00 283 0000 00 281 0628 00 281 0504 00 283 0000 00 281 0504 00 281 0549 00 283 0032 00 281 0504 00 281 0549 00 152 0488 00 152 0488 00 152 0107 00 152 0107 00 152 0141 02 152 0460 00 152 0460 00 152 0141 02 152 0061 00 152 0141 02 152 0061 00 152 0141 02 152 0141 02 152 0141 02 152 0141 02 152 0141 02 150 0109 00 131 0955 00 129 0064 01 129 0064 01 131 0955 00 129 0064 02 129 0064 02 129 0064 00 131 0955 00 129 0064 00 151 0436 00 151 0436 00 151 0347 00 151 0347 00 151 0279 00 151 0350 00 151 0279 00 151 0261 00 151 1010 00 151 0279 00 151 0261 00 1974 Serial Model No Eff Dscont Name amp Description BOARD ASSY MAIN FXD ELCTLT 750UF 75 10 407 CAP FXD ELCTLT 750UF 75 10 40V PXD ELCTLT LOUF 50 10 1007 FXD ELCTLT LOUF 50 10 1007 CAP FXD CER CAP FXD CER CAP PXD CER CAP FXD CER CAP FXD CER CAP FXD CER FXD CER CAP FXD CER CAP FXD CER CAP FXD CER DI 0 001UF 100 0 500V 0 0010 100 0 500 15 5 600 DI 10PF 1PF 500V 0 0010 100 0 500 DI 1
14. A at 25 C lt 2 0nA at 50 C Equivalent Input Drift lt 100 uV C Equivalent Input Noise lt 10 uV RMS SLEW RATE 50 V us into an 800 Q load 1 13 Operating Instructions AM 501 OUTPUT Voltage Range gt 40 V Current Limit gt 50 mA Power Consumption 8 watts SUPPLEMENTAL INFORMATION Power Supplies DC Voltages 49 6 V to t 49 8 V Ripple lt 5 mV measured with a 5 MHz bandwidt oscilloscope i General The AM 501 is a feedback amplifier having low output impedance high overall gain high output voltage and current capabilities and excellent stability The high gain section of the amplifier consists of the input FETs and current sources and the output current sources The output current sources serve as high imped ance loads for the FETs The gain is G where G is the transconductance of the input FETs and R is the impedance of the feedback amplifiers used as signal current sources at the output The output stage is a unity gain amplifier having a very high input impedance and low output impedance The output stage is capable of 40 volts at approximately 50 mA input Amplifier The input FETs use a conventional current source Q125 that provides a constant current determined by the divider R101 R102 R126 and VR126 The source to drain voltage of the input FETs is main tained at a constant value by VR110 and 0110 so that even though the common mode input level may chan
15. Number CB3025 CB2425 CB5105 71035 2 156 0067 00 156 0067 00 iN976B 1 978 1N976B 18821 14821 IN752A 69 6512 69 6512 1N752A
16. R SILICON PNP 07263 2N5401 Q170 151 0188 00 TRANSISTOR SILICON PNP 04713 2 3906 0172 151 0347 00 TRANSISTOR SILICON NPN 80009 151 0347 00 0175 151 0311 01 TRANSISTOR SILICON NPN 04713 40 0180 151 0190 00 TRANSISTOR SILICON NPN 04713 2N3904 Q182 151 0350 00 TRANSISTOR SILICON PNP 07263 255401 0185 151 0311 01 TRANSISTOR SILICON NPN 04713 MJE340 0190 151 0347 00 TRANSISTOR SILICON NPN 80009 151 0347 00 RS 304 0272 00 RES FXD COMP 2 7 OHM 10 1W 01121 682721 R7 304 0272 00 RES FXD COMP 2 7 OHM 10 1W 01121 682721 RLO 311 1562 00 RES VAR NONWIR 2K OHM 20 0 50W 73138 91 20000 R12 311 1562 00 RES VAR NONWIR 2K OHM 20 0 50W 73138 91A 20000M R20 321 0266 00 RES FXD FILM 5 76K OHM 1 amp 0 125W 75042 CEATO 5761F R22 321 0266 00 RES FXD FILM 5 76K 0HM 1 0 125W 75042 5761 R30 321 0355 00 RES FXD FILM 48 7K OHM 1 0 125W 75042 4872 R32 321 0355 00 RES FXD FILM 48 7X OHM 1 0 125W 75042 CEATO 4872F R35 301 0562 00 RES FXD COMP 5 6K OHM 5 0 50W 01121 5625 R37 301 0622 00 RES FXD COMP 6 2k OHM 5 0 50W 01121 6225 R38 315 0473 00 RES FXD COMP 47K OHM 5 0 25W 01121 4735 40 315 0302 00 RES FXD COMP 3K OHM 5 0 25W 01121 CB3025 R42 315 0151 00 RES FXD COMP 150 OHM 5 0 25W 01121 1515 R50 307 0107 00 RES FXD COMP 5 6 OHM 55 0 25W 01121 CB56G5 R52 307 0103 00 RES FXD COMP 2 7 OHM 59 0 25W 01121 2705 R80 303 0122 00 RES PXD COMP 1 2K OHM 5 1W
17. TEKTROND INSTRUCTION MANUAL Tektronix inc Box 500 Beaverton Oregon 97005 Serial Number 070 1616 00 1973 by Tektronix Inc Beaverton Ore 22 Printed in the United States of America rights reserved gt Contents of this publication may not be reproduced in any form without permission of Tektronix inc U S A and Foreign TEKTRONIX products covered by U S and foreign patents and or patents pending 2 Section 1 501 OPERATING INSTRUCTIONS INTRODUCTION instrument Description The AM 501 is a high power operational amplifier unit designed for use in the TM 500 series power modules The unit has a wide output voltage swing centered at zero high common mode range and a high stewing rate The AM 501 has convenient front panel access terminals for connection of feedback resistors to either input or various input loading configurations Internai pads on the circuit board permit permanent loading feedback or input component connections front panel switch permits selective grounding of either BNC input or binding post connectors The output may be taken from front panel binding posts or a BNC connector POWER MODULE installation and Removal The AM 501 is calibrated and ready for use when received It operates in any compartment of a TM 500 series power module See the power module instruction manual for line voltage requirements and power module o
18. constants involved in shunt capacitance Cy and Cj are approximately 4 Figs 1 12 through 1 14 illustrate the corrections nec essary to improve accuracy for each of the basic operations Errors Due To Signal Source Impedance A part of Zi the input element of the operational amplifier circuit is the source impedance of the signal being processed Linear operations using precision input and feedback components will be accurate only if the source impedance of the signal is very small compared to the impedance of the input component The value of the input or feedback component may also be trimmed to allow for the impedance of the signal source Compensated Differentiator Without compensation the differentiator may respond to a sudden change in dEin dt by overshoot followed by sinusoidal ringing This is because excess output voltage must be developed to charge the input capacitance via Rr plus the distributed stray capacitance of Rt itself Current is also required to obtain a null at the minus input As soon as the stray capacitances are charged excess current through Ri upsets the null and the output must swing in the opposite direction to re establish the null and discharge the capacitance associated with Rf This produces the ringing A small capacitance across Rf Fig 1 13 provides the 1 9 pee Operating Instructions AM 501 et Wideband Amplifier Correction for Stray Capacitance ec
19. duced Using Standard Waveforms For Comparison The use of a standard waveform pulses and ramps with known parameters is of considerable help in adjusting compensation and ensuring best accuracy for critical measurements near the limits of the instrument capabilities Selection of time and amplitude parameters close to those of waveforms to be measured gives best assurance against possible system errors The integrating interval t4 to t2 has been mentioned several times Frequently it is desired to integrate repetitive signals that are not perfectly symmetrical about zero volts This causes a DC voltage accumulation that will eventually drive the operational amplifier to its limit Therefore some means is required that returns the output to zero after time t the end of the integrating interval For slow work a pushbutton switch that can discharge 24 manually is usually sufficient When the integrating interval is quite short compared to the signal period low duty factor RC networks may be placed around 2 to return the output level to O volts through a time constant much longer e g 100X than the integrating interval For sine waves the gain of the integrator varies inversely with frequency the actual gain being 1 27fRC except as limited by the open loop gain at low frequencies and the open loop gain bandwidth product at high frequencies At low frequencies the gain becomes less than the formula 1 11 Ope
20. enses the rate of change at the input This operation is differentiation sensing input voltage rate of change and providing an output voltage that is proportionate to that rate of change The actual relationship of output to input is Eout dEin dt X RC The expression dEin dt indicates the rate of change of input voltage out RC Operating Instructions AM 501 out o Y Operational Amplifier as Differentiator Output is proportional to dE di Fig 1 6 Operational Amplifier as a Differentiator rate of change in volt seconds of the input signal at any given instant while the R and C are the Z and Zi respectively The example uses a constant rate of change and a constant voltage output is obtained if the rate of change is not constant the output signal voltage shows this dramat ically with wide variations in amplitude The differentiator senses both rate and direction of change It is a useful device for detecting small variations of slope or discontin uities in waveforms Integration If the resistor and capacitor used for differentiation are interchanged Fig 1 7 the circuit characteristics are exactly opposite The output signal becomes a rate of change that s proportional to the input voltage This is integration because the instantaneous value of the output voltage at any time is a measure of both amplitude and duration up to that time of the input signal The operational am
21. ge the FET characteristics remain constant CR100 and R100 provide impedance at the drain of Q120 A plus input equivalent to the impedance at the drain of 01208 minus input 105 is the current source for VR110 0125 provides about 6 mA and Q105 needs about 2 mA This leaves about 4 mA for 0120 Thus when 0120 is balanced 2 mA flows through each side of 0120 VR126 R101 R102 R105 R125 and R126 set a relationship between current sources 0105 and 0125 so that any current change in one is matched by an equal change in the other This keeps the total current in Q120 constant and thus maintains amplifier stability with tem perature and supply voltage variations e Section 2 AM 501 THEORY OF OPERATION The 2 flowing through Q120A also flows through common base stage Q100 providing 2 mA to the controlled signal current source 0130 and 0135 The same condition exists in the 0115 0140 side of the amplifier which supplies 2 mA through 0140 to 0145 and Q150 Differences in characteristics of the active components are balanced out using the Offset Null controt R122 0130 and 0135 and their counterparts O145 and 0150 act as signal current sources Any voltage change at the base of Q135 causes equal current changes in Q130A and 130 since they are matched transistors The same is true for 0145 0150 and 0150 Although the current through Q135 is fairly insensitive to collector voltage slightly more cu
22. ig 1 3 shows pad layouts for internal component connections Any combination of resistors capacitors or other components may be soldered to the pads as required Jumper from the Input Output and Ground connections labeled on the board to the appropriate pads If necessary remove the wires to the front panel connections and re connect them to the pads If more than a foot or two of coaxial cable is used at the output an isolation resistor equal to the cable impedance should be connected between the amplifier OUTPUT terminal and the center conductor of the coaxial cable to prevent ringing This resistor may conveniently be con nected between J175 lower OUTPUT binding post and J176 OUTPUT BNC connector A transparent window with removable information slide is provided for noting the connections made to the AM 501 To remove the slide grasp the sectioned sub panel on the right side of the instrument and pull Attach a gummed label to the slide and draw on the label the connections made 1 2 Jumper Across Pads For Appropriate Connections n Fig 1 3 Pad layouts for internal connections Operating Instructions AM 501 APPLICATION CONSIDERATIONS Introduction Operational amplifiers such as the AM 501 are useful in simulating a variety of circuits They are used to add subtract differentiate integrate and amplify either lin early or with controlled non linear coefficients under signal c
23. istive feedback circuit the input impedance appears as the resistance of the feedback element divided by the open circuit gain of the amplifier 2 2 Current applied to the minus input tends to develop voltage across the impedance of the feedback element and move the minus input away from ground The output of the amplifier however swings in the opposite direction and provides current to balance the input current This effec tively holds the minus input at ground potential If the impedance of the feedback element Zt is high a high output voltage is required to provide even a smal feedback current Since most applications deal with voltage signals an additional element called input impedance Zt is used This impedance in series with the minus input converts that parameter of the input signal appearing as voltage into current See Fig 1 4C Gain The current through Zi is equal to the applied voltage at point A Fig 1 5 divided by the impedance of Zi or Ein Zi Previously it was stated that this exact value of current must flow through Zf to keep point at ground potential The voltage output at point C therefore must equal the current Ein Zi through Zf muitiplied by the impedance of Zf Since the output signal is the inverted input it becomes Ein Zi Zf and the voltage gain of the operational amplifier becomes Eout Ein or Zt Zi 14 Operational amplifier using resistors for both Z and Z becomes fixed
24. ley Co Motorola Inc Semiconductor Products Div Fairchild Semiconductor A Div of Fairchild Camera and Instrument Corp Teledyne Semiconductor and Components Inc National Semiconductor Corp Teledyne Semiconductor Specialty Connector Co Inc Sprague Electric Co Superior Electric Co The Chicago Miniature Lamp Works Erie Technological Products Inc Beckman Instruments Inc Helipot Div TRW Electronic Components IRC Fixed Resistors Philadelphia Division Tektronix Inc Beckman Instruments Inc International Rectifier Corp ADDRESS 1201 2nd St South 5005 E McDowell Rd 464 Ellis St 12515 Chadron Ave 103 Morse Street Commerce Drive 1300 Terra Bella Ave 3560 Madison Ave 383 Middle St 4433 Ravenswood Ave 644 W 12th St 2500 Harbor Blvd 401 N Broad St 0 Box 500 2500 Harbor Blvd 9220 Sunset Blvd CITY STATE ZIP Milwaukee WE 53204 Phoenix AZ 85036 Mountain View CA 94042 Hawthorne CA 90250 Watertown MA 02172 Danbury CT 06810 Mountain View CA 94040 Indianapolis IN 46227 North Adams 01247 Bristol CT 06010 Chicago IL 60640 Erie PA 16512 Fullerton CA 92634 Philadelphia PA 19108 Beaverton OR 97077 Fullerton C 92634 Los Angeles CA 90069 REV B SEP 1974 Ckt No Ai clo C12 C20 C22 100 105 2116 C118 Ci25 C165 C167 C175 C190 2192 CRLO CR12 CR60 CR62 CRLOO CRI20 CRL24 CRi30 CR135 CR13
25. nd but as the gate to drain breakdown of 0120 is reached current limiting diode CR120 124 limits the input current to 1mA protecting the FET Below this point CR120 CR124 behaves as a low value resistor approximately 1 to 2 C118 and R119 prevent oscillation at the higher frequency limits C116 improves the slewing rate during high common mode voltage swings The bandwidth may be reduced if desired by the addition of capacitance at Points 1 and 2 See the Controls Connectors and Adjust ments foldout for locations Output Amplifier The Output Amplifier is unity gain voltage follower impedance transforming amplifier 0170 is an emitter follower having a current source from 0165 feeding two successive emitter followers 0172 0175 0180 is an emitter follower having current source from 0190 feeding a unity gain feedback amplifier 0182 and 0185 The algebraic sum of the diode and base emitter drops around the loop starting at the collector of 0185 the emitter of 0182 and progressing clockwise to the emitter of Q175 is slightly greater than zero These voltage drops are impressed across R175 and R185 to fix the standing current in the output transistors With the input FET gates tied together the output voltage at the junction of R175 R185 is zero R168 and R193 are part of a current limiting circuit As the load current increases to a value near the limit the drop across R168 causes CR16
26. o Assume that an input signal for integration is a 1 volt positive pulse for a period of 1 second Fig 1 8 The sum of all voltage periods from t4 t is one volt second With a Zi Z combination of 1 and 1 the output voltage Eo will fall at a rate of 1 volt second times Ein RC fora period of 1 second The output voltage will reach 1 volt at the end of the input pulse time period and remain at this level This is often referred to as taking the area under the curve since the area under the waveform plotted against time i e the area bounded by t4 t2 the amplitude of the waveform and the O line is the number of volt seconds involved In addition the instantaneous value of Eout at any time is proportional to the input volt seconds to that selected time The preceding example used an RC of 1 1X 10 X 10 and the numerical value of the output voitage at the end of the integrating period was the number of volt seconds in the input waveform Other values of R and C will require additional calculation to find the input volt seconds The Ta T iv Output Indicates one volt second input Fig 1 8 Simple case of integrating 1 volt second pulse The integrator does not improve measurement accuracy in so simple a case 1 6 g D output voltage must be multiplied by RC For example if R is 200 000 2 C is 0 01 uF and the output after the selected period is 2 5 volts then multipivina
27. onditions By using semiconductors or other external active elements operational amplifiers will perform com The input is to the base of the triangular symbol the output is from the apex opposite The input and output are out of phase arrows b Feedback element 2 provides the negative feedback to permit high accuracy operations The amplifier seeks a null at the input by providing feedback current through Z equal and opposite to the input current lin Output voltage is whatever is necessary to provide required bafancing current through Z pression expansion root and power functions limiting clipping and fast response logarithmic amplification The following text and illustrations will show some basic operational amplifier concepts and functions The reader is referred to the many excellent books available concerning various uses and applications for operational amplifiers See Fig 1 4 for basic operational amplifier symbols Ovtput c input element Z converts a voltage signal E to current which is balanced by current through Z NOTE It is convenient to represent high gain dc operational amplifiers by a triangular figure as shown The base of the triangle is the input the apex s the output For most operations the negative input which produces a positive going output for a negative going input is used and the positive input is grounded Where the input is not identified or
28. pare the approximate error The error is found by the formula Eout 71 more simply 1 1 e where is the open loop gain and Eout Ein is the actual voltage gain Remember that both A and Eout Ein are negative numbers For example when A is 10 000 and the observed Eout Ein is 500 the error is 501 10 001 or 6 095 The output 500 then represents 94 905 of the correct value and the correct value is 500 0 94905 approximately 527 For convenience the terms may be arranged as follows to determine how large an output signal may be allowed for a given input and an arbitrarily selected maximum error Max Eout 1 e 1 lt is Important to remember that A is not constant but changes with frequency in accordance with the gain bandwidth product Compensation For The Effect Of Stray Cap acitance Accuracy in high speed operations will be affected by shunt capacitance Cs and by the distributed capacitance around Zi and 26 Fig 1 11 Their effect is more pronounced at higher frequencies where the effective value of A is low Operating Instructions AM 501 Fig 1 11 Where Z or Z4 is a resistor and particularly if a large gt 100 k value more serious errors may be caused by capacitance from the resistor body highest impedance point to ground and in the case of R during integration end to end pacitance of Ri Time
29. peration Fig 1 1 shows the AM 501 installation and removal procedure ut Turn the Power Module off before insert ng the plug in otherwise damage may occur to the plug in circuitry Check that the AM 501 is fully inserted n the power module Pull the PWR switch on the power module The Connectors and Adjustments foldout page in Section 3 gives a complete description of the front panel Groove Fig 1 1 501 Installation and Removal REV 1975 1 1 Operating Instructions AM 501 BASIC OPERATION Input Output and Feedback Connections Make connections to the operational amplifier through the front panel binding posts the BNC connectors or the rear interface connector The rear interface connections are not factory wired See Fig 1 2 for suggested pin numbers ASSIGNMENTS and functions Pads are provided on the circuit board for the pins shown A barrier inserted between pins 23 and 24 in the power module will allow the AM 501 and plug ins compatible with it to be inserted in that compartment See the power module manual for more information ASSIGNMENTS FUNCTION CONTACT CONTACT FUNCTION 2B A SIGNAL OUT iii 2 GROUND GROUND 258 3 SIGNAL 24 GROUND 22B SIGNAL IN 21 gt NOTE These connections are not factory wired Fig 1 2 Input Output assignments for plug in rear interface connector contacts F
30. plifier operates as an integrator in the following manner Assume a Zi of 1 Zt of 1 uF and an Operational Amplifier as integrator Output rate of change is Substituting for ei in the preceding equation proportional to input voltage 1 1 Ein sin wt dt or R C Ji Ein dt RC in the example here is 1 second Output then is 1 volt per Ed os second per volt input and most importani the output level at Ri Ci anytime is one volt per volt second input 605 where E is the peak amplitude 0 is the angular frequency and integration tends to eliminate the high frequency components in is time a waveform This is because the output voltage from the integrator is inversely proportional to the frequency of the input This can be seen if we assume sinusoidal input waveform of the form ei E This equation shows that the output voltage is inversely proportional to the frequency of the input signal Fig 1 7 Operational Amplifier as an Integrator Operating Instructions AM 501 input signal of zero With these conditions no balancing current is required through Zf so the output voltage remains at zero Suppose that a 1 volt DC signal is applied to Zi This will require a balancing current of 1 uA through 7 To produce this 1 balancing current through a Zt of 1 uF a continually rising voltage must be generated at the output having a rate of rise
31. rating Instructions AM 501 would indicate the effect becoming noticeable at the point Practical Circuits where the formula indicates a gain of approximately 1 3 the open loop gain At high frequencies the error becomes significant above approximately 1 10 of the open loop Figs 1 15 through 1 19 show several practical circuit gain bandwidth product Except as limited above the applications for the 501 These circuits illustrate the integrator shifts the phase of the input sine wave by 90 many possible uses for the AM 501 Fig 1 15 1 Non inverting amplifier follower Fig 1 16 X5 Non inverting amplifier Fig 1 17 X1 inverting amplifier Fig 1 18 X5 inverting amplifier 1 12 6 Integrated Operationai Amplifier 15 Operating instructions AM 501 tk 1 8 W 15 1 uA741C For precise adjustment of OFFSET level a 10 turn pot and dial combination is recommended Fig 1 19 X5 Amplifier with offset SPECIFICATIONS Performance Conditions The electrical characteristics are valid only if the AM 501 is calibrated at an ambient temperature between 20 and 30 C and operated between 0 C and 50 C GAIN Open Loop 210 000 into 800 52 load COMMON MODE REJECTION RATIO 210 000 to 1 at 60 Hz UNITY GAIN BANDWIDTH 25 MHz into 800 0 load INPUT Maximum Safe Differential Input Voltage 80 V Common Mode Input Voltage Range 40 V Input Leakage Current lt 500 p
32. rrent will flow through Q135 and 1308 when Q135 s collector is more negative This increased current passing through O130B causes equally increased current flow in Q130A making its collector go more positive and reducing the additional current through Q135 Again the identical action takes place 0145 and 0150 only the polarities are different Thus for a given signal current change at the base of 0135 and 0145 the output current at the collectors of 0135 and 0145 changes proportionally This current change is nearly independent of the voltage at the collectors of O135 and Q145 The drains of the input FETs see an effective load impedance of approximately 10 MQ This configuration also provides single voltage amplification point and a single RC ampli tude vs frequency rolloff characteristic These factors are necessary to prevent oscillation when using 10096 feedback CR130 and CR135 CR140 CR145 prevent saturation of 0135 0145 when full differential voltage is applied at the input VR135 and VR140 limit the voltage at the common output point preventing saturation in the output amplifier CR 137 is a voltage dropping diode used to compensate for inequality in junction drops from side to side in the output amplifier 2 1 Theory of Operation AM 501 No harm can be done to the input even if the input drive is maximum 440 V and 40 V The range of the amplifier will have been exceeded it will be locked up at one e
33. the following information in your order Part number instrument type or number serial number and modification number if applicable if a part you have ordered has been replaced with a new or improved part your local Tektronix Inc Field Office or representative will contact you concerning any change in part number Change information if any is located at the rear of this manual SPECIAL NOTES AND SYMBOLS X000 Part first added at this serial number 09X Part removed after this serial number ITEM NAME in the Parts List an Name is separated from the description by a colon Because of space limitations an Name may sometimes appear as incomplete For further Name identification the U S Federal Cataloging Handbook H6 1 can be utilized where possible ABBREVIATIONS ACTR ACTUATOR PLSTC PLASTIC ASSY ASSEMBLY QTZ QUARTZ CAP CAPACITOR RECP RECEPTACLE CER CERAMIC RES RESISTOR CKT CIRCUIT RF RADIO FREQUENCY COMP COMPOSITION SEL SELECTED CONN CONNECTOR SEMICOND SEMICONDUCTOR ELCTLT ELECTROLYTIC SENS SENSITIVE ELEC ELECTRICAL VAR VARIABLE INCAND INCANDESCENT WW WIREWOUND LED LIGHT EMITTING DIODE TRANSFORMER NONWIR NON WIREWOUND XTAL CRYSTAL REV B SEP 1974 Electrical Parts List AM 501 CROSS INDEX MFR CODE NUMBER TO MANUFACTURER MFR CODE 01121 04713 07263 07910 09353 12040 15818 24931 56289 58474 71744 72982 73138 75042 80009 80740 81483 MANUFACTURER Allen Brad
34. uld hold the null at exactly zero volts and the impedance would be exactly zero ohms The practical amplifier having finite gain does not quite null the minus input to zero ohms but moves 1 A times the output voltage swing A Open loop gain of the amplifier Ein Eout A The input impedance therefore appears as the quantity 2 1 A See Fig 1 9 NOTE The input impedance at the minus input is obtained by the following mathematical derivation Ein Ein Eout and lin lin Zt Since Zin Operating instructions AM 501 Fig 1 9 Apparent impedance at the input Ein then Zin Ein Eout which equals Zt Eout ie Eout Em 1 A A 24 If the voltage swing Eout A is a significant fraction of the input signal Ein or if the impedance 2 1 is a significant fraction of Zi there will be a definite error in the output signal which adds to the error introduced by the tolerances of the passive elements Zi and Z The exact value of this error is 1 1 If the ratio of 2 21 is small and A is large this error is not serious Shunt Impedance Across The Minus input The true impedance from the minus input to ground is Zt 1 and with large values of A is a very low value calculated as virtual ground However when A becomes small and Zt becomes large the shunt impedances particu larly capacitive reactance can interfere with the operation See Fig 1 1
35. width Product The gain factor A of the operational amplifier decreases with an increase in frequency therefore it is important to know the effective value of A for the frequencies in use The error introduced by this decrease becomes signifi cant at higher frequencies Consequently to make accurate measurements the allowable ratio of Eour Ein must be reduced when higher frequency information is processed When the input frequency is approximately 1 10th the unity gain bandwidth frequency open loop gain is approxi mately 10 and is not sufficient to provide accuracy better than 9 even with a closed loop gain of unity Moreover the effects of added integrating components from input and feedback elements cause even more roll off so the closed loop gain frequency characteristics become less than 3 the theoretical limit Hence for critical applications compensation to the nominal values of Zi and 2 is recommended to reduce the gain factor error It is well to note that except in the case of straight amplification Fig 1 10 the compensation introduces possible errors that must be recognized and considered in the interpretation of the results Accuracy With Capacitors Used For Zi Or 24 Since it is not easy to assign a single impedance value in the error formula for Zi or Zt when either is a capacitor it is convenient to use the ratio Eout Ein to represent the actual voltage gain in order to com
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