ECE 1270: Introduction to Electric Circuits Lecture 13: Operational Amplifiers Part 1 Chapter 5 The Operational Amplifiers Sections 5.1,5.2, 5.3

Operational Amplifiers Purpose 1) Amplify AC/DC voltage (or current). 2) Perform addition, subtraction, multiplication, division, differentiation, and integration of signals

Operational Amplifiers: Applications 1) Amplify audio signals 2) Filter unwanted signals (frequencies) 3) And many more... Subwoofer Filter Audio Preamplifier

Operational Amplifiers Pin Diagram Positive Power Supply Negative Power Supply

Operational Amplifiers Symbol & Notation ip io in

OpAmp: Circuit Model vp vo vn vp vo vn Open loop gain Output voltage in linear region vo vn Open loop gain (without feedback) vp Input Resistance Output Resistance vo + - vn

OpAmp Characteristics vp vo + vn - An Ideal Op amp has infinite open-loop gain, infinite input resistance and zero output resistance When Op amp is connected in the circuit... For an ideal OpAmp vp = vn (voltages at positive input terminal and negative input terminal are equal to each other) ip= in = 0 (currents entering the positive and negative input terminals are zero) vp ip vo vn in

Example 5.1 a) Find vo if va=1 V, vb=0 V Simulate: 1) with va=1V and 2) with va=2Vpp@1kHz

AP5.1 a) a) Find vo if vs=0.4, 2.0, 3.5, -0.6, -1.6, -2.4 Q: Which values of vs will cause op amp to saturate?

p5.4 a) & (b) a) Find vo if va = 1.5 V and vb = 0 V 40 5 2 10 a) Find vo if va = 1.5 V and vb = 0 V b) Find vo if va = -0.5 V and vb = 0 V

Op-Amp Configurations 1) Inverting Amplifier 2) Non-inverting Amplifier 3) Voltage Follower (or buffer) 4) Summing Amplifier 5) Difference Amplifier

Inverting Amplifier 1) Output and Input signals have opposite polarity (180 ° phase shift) 2) Inverting Amplifier provides negative voltage gain

Example 5.2: Design of an Inverting Amplifier

p5.8: Design of an Inverting Amplifier