Download presentation

Published byIsabel Lee Modified over 4 years ago

1
**Lecture 4 Operational Amplifiers—Non-ideal behavior**

1

2
**Goals Study non-ideal op amp behavior.**

Demonstrate circuit analysis techniques for non-ideal op amps. Understand frequency response limitations of op amp circuits. 2

3
**Frequency Response of Op Amps: General Case**

vo = A (v+ - v-) (A) is function of frequency General purpose op-amp has a single-pole response 100db Gain = 105 0 dB Gain = 1 3 Band-width Unity gain frequency

4
**Frequency Response of Op Amps: General Case**

Op amps: Low-pass amplifier with high gain at dc and a single-pole frequency response. wB = open loop bandwidth of op amp. ωT = unity gain bandwidth (frequency at which magnitude of gain is unity). At w >>wB, At ω =ωT, At w >>wB,product of magnitude of amplifier gain and frequency is a constant value of unity gain frequency. Hence, wT is also called gain-bandwidth product. 4

5
**Frequency Response of Op Amps: General Case (Example)**

Frequency values are often expressed in Hz. Problem: Find transfer function describing frequency-dependent amplifier voltage gain. 5

6
**Frequency Response of Op Amps: Noninverting Amplifier**

6

7
**Frequency Response of Op Amps: Noninverting Amplifier**

|Vo/Vin| (dB) Ao -20 dB/dec 1 + R2/R1 f (log scale) f3dB (no feedback) f3dB (with feedback) 7

8
**Gain = 105 (100dB) f3dB = 1MHz/105 = 10 Hz **

For a 741 Op amp, ft = 1MHz Gain = 105 (100dB) f3dB = 1MHz/105 = 10 Hz Gain = 100 (40 dB) f3dB = 1MHz/100 = 10KHz Gain = 10 (20dB) f3dB = 1MHz/10 = 100KHz 8

9
**Frequency Response of Op Amps: Noninverting Amplifier (Example)**

Problem: Characterize frequency response of noninverting amplifier. Given data: Ao= 105= 100 dB, fT= 107 Hz, desired Av= 1000= 60 dB Assumptions: Amplifier is described by single-pole transfer function. Analysis: Noninverting amplifier transfer function 9

10
Slew Rate (SR) Slew rate: maximum rate of change at the output of the OPAMP 10

11
**Large Signal Limitations: Slew Rate (SR) and Full-Power Bandwidth**

Slew rate: Maximum rate of change of voltage at output of op amp.Typical values range from 0.1V/ms to 10V/ms. For given frequency, slew rate limits maximum signal amplitude that can be amplified without distortion. For no signal distortion, Full-power bandwidth is highest frequency at which a full-scale signal can be developed. 11

Similar presentations

OK

1 CHAPTER 20 OPERATIONAL AMPLIFIERS (OP-AMPS). 2 Introduction to operational amplifiers Symbol and Terminals.

1 CHAPTER 20 OPERATIONAL AMPLIFIERS (OP-AMPS). 2 Introduction to operational amplifiers Symbol and Terminals.

© 2018 SlidePlayer.com Inc.

All rights reserved.

To make this website work, we log user data and share it with processors. To use this website, you must agree to our Privacy Policy, including cookie policy.

Ads by Google