1 / 32

MALVINO & BATES

MALVINO & BATES. Electronic PRINCIPLES. SEVENTH EDITION. Chapter. 22. Nonlinear Op-Amp Circuits. Topics Covered in Chapter 22. Comparators with zero reference Comparators with non-zero references Comparators with hysteresis Window comparator The integrator Waveform conversion.

hilel-snider
Download Presentation

MALVINO & BATES

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. MALVINO & BATES Electronic PRINCIPLES SEVENTH EDITION

  2. Chapter 22 Nonlinear Op-Amp Circuits

  3. Topics Covered in Chapter 22 • Comparators with zero reference • Comparators with non-zero references • Comparators with hysteresis • Window comparator • The integrator • Waveform conversion

  4. Topics Covered in Chapter 22(Continued) • Waveform generation • Another triangular generator • Active diode circuits • The differentiator • Class D amplifier

  5. Comparators with zero reference • Called zero-crossing detectors • Diode clamps used to protect comparators against large inputs • Usually interface their outputs with digital circuits

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

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

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

  9. Comparators with non-zero references • Sometimes called limit detectors • Op amps may be used • IC comparators are optimized by removing the internal compensating capacitor which increases switching speed

  10. R2 Vref = (−VEE) R1+R2 Non-inverting threshold detector +VCC vin vout R2 . -VEE R1 vin Vref +Vsat vout -Vsat

  11. 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.

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

  13. Comparators with hysteresis • Noise is any unwanted signal not related to the input • Noise can cause false triggering • Positive feedback creates hysteresis • Hysteresis prevents false triggers and speeds up switching

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

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

  16. Window comparator • Called a double-endedlimit detector • Detects when the input voltage is between two limits • Uses two comparators with two different trip points

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

  18. Integrator • Useful for converting rectangular pulses into linear ramps • Earliest part of exponential charge is used • Output ramps are almost perfect • Used to create time bases for oscilloscopes

  19. T -T V = vin RC V Integrator circuit 10R . R C . vin vin vout 0 0 vout

  20. Waveform conversion • A Schmitt trigger can be used to convert a sine wave to a rectangular wave • An integrator can convert a square wave to a triangular wave • The duty cycle of a limit detector can be controlled with an adjuster resistor

  21. VP vout(pp) = 2fRC Rectangular to triangular converter 10R . R C . vin +VP vout vin -VP vout

  22. R2 Vref = VCC R1+R2 Vref Triangle to pulse converter vin vout R2 . +VCC R1 vin vout

  23. Waveform generation • Oscillators require no external input and still generate an output signal • Oscillators work because of positive feedback • A relaxation oscillator uses a charging capacitor • A triangular waveform is produced by cascading a relaxation oscillator and an integrator

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

  25. Triangular waveform generator R5 C2 . R3 . . R4 . C1 vout . R2 R1

  26. R1 R2 UTP = Vsat R2 f = 4R1 R3 C Another triangular waveform generator R2 R4 . . . R3 .. C . vout R1 Schmitt trigger and cascaded integrator H = 2UTP Vout(pp) = H

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

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

  29. Active positive clamper . . 0 vin RL 0 An op amp with negative feedback allows the clamping of signals with amplitudes less than the diode knee voltage.

  30. Differentiator • When a square wave drives an RCdifferentiator, the output is a series of narrow positive and negative voltage spikes • Using an op amp will improve the differentiator and provide a low output impedance

  31. Differentiator circuit and operation R . C vin . vout 0.01R to 0.1R

  32. Class D amplifier • Uses output transistors as switches • These transistors are alternately driven into saturation and cutoff by the output of a comparator • Provides very high circuit efficiencies • Popular in portable equipment

More Related