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MALVINO

SIXTH EDITION. MALVINO. Electronic. PRINCIPLES. Linear Op-Amp Circuits. Chapter 20. -R 2. A V =. 1. 1. f unity. R 1. f 2 =. 2 p R L C 2. 2 p R 1 C 1. R 2. +1. R 1. f c1 =. f c2 =. ac coupled inverting amplifier. R 2. C 1. R 1. C 2. v in. R L. v out. R 1 R + R 2.

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MALVINO

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  1. SIXTH EDITION MALVINO Electronic PRINCIPLES

  2. Linear Op-Amp Circuits Chapter 20

  3. -R2 AV = 1 1 funity R1 f2 = 2pRLC2 2pR1C1 R2 +1 R1 fc1 = fc2 = ac coupled inverting amplifier R2 C1 R1 C2 vin RL vout

  4. R1 R + R2 -R2 R1 R1 R Adjustable bandwidth R2 R1 vout vin B = A R f2 = Bfunity f

  5. 1 2pR1C3 fc3 = ac coupled noninverting amplifier C1 C2 vin R3 R2 RL vout Bdc = 1 R1 C3

  6. JFET controlled inverter/noninverter R R vout R vin 0 V VGS(off)

  7. Adjustable gain of ± 1 R R vout vin

  8. f Phase shifter R’ R’ vout vin R C t f = -2 arctan 2pRCf

  9. Ideally: DR DR R1 = R1’ R R -R2 AV = R2 = R2’ R1 ±2 < ACM < ±4 Differential amplifier R1 R2 vin(CM) vin vout vin(CM) R2’ R1’ CMRR limiting factors are the op amp itself and the tolerance of the resistors.

  10. Transducer Wheatstone bridge +V R1 R3 vout R2 R4

  11. Wheatstone bridge • The differential output signal is small. • The common-mode output signal is large. • Differential amplifiers are a good match. • Transducers convert nonelectrical quantities into an electrical quantity such as resistance: • examples: photoresistor, thermistor, strain gage

  12. Instrumentation amplifiers • Differential amplifiers optimized for dc performance • Large differential voltage gain • High CMRR • Low input offsets • Low temperature drift • High input impedance

  13. DR R -2R1 +1 AV = RG ±2 ACM = Instrumentation amplifier vin(CM) R R R1 vin RG vout R1 R R vin(CM)

  14. Monolithic instrumentation amplifiers • Use laser-trimmed resistors for high performance. • Resistor RG is external and is selected to set the differential gain. • Resistor RG can be split into two devices for guard driving (bootstrapping the cable shield to the common-mode potential).

  15. RG RG 2 2 Guard driving Instrumentation amplifier vout Guard voltage (common-mode voltage)

  16. Summing amp with inverting and noninverting inputs RF R1 v1 v2 vout R2 R3 v3 R5 v4 R4

  17. 1 vin 8 N = 4 D/A converter R R v3 2R v2 vout 4R v1 8R v0 vout = -(v3 + 0.5v2 + 0.25v1 + 0.125v0) Possible combinations = 2N = 24 = 16

  18. Unidirectional current booster +VCC vin bdc = 100 741 R2 vout RL R1 Imax = bdcISC = 100(25 mA) = 2.5 A

  19. Bidirectional current booster R2 +VCC R1 vin vout RL -VEE

  20. AGC circuit R1 R5 R2 vin vout Voltage-controlled resistance R6 +VAGC As the signal level increases, VAGC goes more positive. As the JFET rds drops, the input signal is attenuated. R3 R4 -VEE

  21. +VCC 2 Single-supply inverting amplifier R2 +VCC C1 R1 C2 vin RL vout R C3 R

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