1. MALVINO
Electronic
PRINCIPLES
SIXTH EDITION

2. Nonlinear Op-Amp Circuits
Chapter 22

3. Inverting comparator
+VCC
100,000
vin
Diode clamps
for protection
vout
-VEE
vin
+Vsat
-Vsat
vout

4. The trip point of a zero-crossing detector should be near zero volts.
Inverting comparator with input bias compensation
vout
vin
+VCC
-VEE RB

5. Bounded output zero-crossing detector
+VCC
vin
vout
-VEE
vin
+VZ + 0.7
-VZ - 0.7
vout

6. Non-inverting threshold detector
+VCC
vin
vout R2 R2
R1+R2
VT =
VEE
-VEE R1
vin VT
+Vsat
vout
-Vsat

7. IC comparators
Op amps have speed limitations due to the internal compensation capacitor.
Comparator ICs are optimized for non-linear operation so the capacitor is not needed.
Comparator ICs often have open-collector outputs to make interfacing more flexible.

8. Using a pullup resistor with an open-collector output stage+V
pullup
vout
IC comparator
When the
transistor
is off, the
resistor pulls
vout up to +V.

9. The Schmitt trigger uses positive feedback
R1+R2
B =
+VCC
vin
vout
UTP = BVsat
-VEE R1
LTP = -BVsat R2
H = 2BVsat
UTP
vin
LTP
+Vsat
vout
-Vsat

10. vin +Vsat vout -Vsat UTP vin LTP +Vsat vout -Vsat
Comparing a zero-crossing detector to a
Schmitt trigger when both have noisy input signals.
UTP
vin
LTP
+Vsat
vout
-Vsat

11. Window comparator +VCC vout LTP +Vsat D1 vin -VEE vout LTP HTP vinRL D2
Output is low
when input is
in window
HTP
-VEE

12. Integrator
10R R C
vin
vin
vout T
V = vin -T RC
vout V

13. Rectangular to triangular converter
vin
+VP
vout
vin
-VP
vout(pp) =
2fRC VP
vout

14. Triangle to pulse converter
vin
vout R2 R2
R1+R2
VT =
VCC VT
+VCC R1
vin
vout

15. Relaxation oscillator
vout C
UTP
LTP vC R2 R1
vout
T = 2RCln
1+B
1-B

16. Triangular waveform generatorC2 R3 R4 C1
vout R2 R1

17. Another triangular waveform generatorC
vout R1 R1 R2
Vsat
UTP = R2
4R1 R3 C
f =
H = 2UTP
Vout(pp) = H

18. Active half-wave rectifier
vin RL VK
VK(CL) =
AOL
An op amp with negative feedback allows the rectification
of signals with amplitudes less than the diode knee voltage.

19. Active peak detector with reset
RLC > 10T
vin C RL
Reset

20. Active positive clamper
vin RL
An op amp with negative feedback allows the clamping
of signals with amplitudes less than the diode knee voltage.

21. Differentiator R C
vin
vout
0.01R to 0.1R