1. MALVINO
Electronic
PRINCIPLES
SIXTH EDITION

2. Linear Op-Amp Circuits
Chapter 20

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

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

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

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

7. Adjustable gain of ± 1 R R
vout
vin

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

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

10. Wheatstone bridge +V R1 R3
vout
Transducer 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. Instrumentation amplifier
vin(CM) R R R1
vin RG
vout R1 R R
vin(CM)
AV =
-2R1 RG +1 ±2 DR R
ACM =

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

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

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

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

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

20. AGC circuit R5 R1 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. Single-supply inverting amplifier
+VCC C1 R1 C2
vin RL
vout R C3 R
+VCC 2