EE 1270 Introduction to Electric Circuits Suketu Naik 0 EE 1270: Introduction to Electric Circuits Lecture 13: Operational Amplifiers Part 1 Chapter 5 The Operational Amplifiers Sections 5.1,5.2, 5.3

EE 1270 Introduction to Electric Circuits Suketu Naik 1 Operational Amplifiers Purpose 1) Amplify AC/DC voltage (or current). 2) Perform addition, subtraction, multiplication, division, differentiation, and integration of signals

EE 1270 Introduction to Electric Circuits Suketu Naik 2 Operational Amplifiers: Applications 1) Amplify audio signals 2) Filter unwanted signals (frequencies) 3) And many more... Audio Preamplifier Subwoofer Filter

EE 1270 Introduction to Electric Circuits Suketu Naik 3 Operational Amplifiers Pin Diagram Positive Power Supply Negative Power Supply

EE 1270 Introduction to Electric Circuits Suketu Naik 4 Operational Amplifiers Symbol & Notation ipip inin ioio

EE 1270 Introduction to Electric Circuits Suketu Naik 5 OpAmp: Circuit Model vpvp vpvp vnvn + - vnvn vovo vovo Open loop gain (without feedback) Input Resistance Output Resistance Output voltage in linear region

EE 1270 Introduction to Electric Circuits Suketu Naik 6 OpAmp Characteristics vpvp + - vnvn vovo vpvp vnvn vovo When Op amp is connected in the circuit...  For an ideal OpAmp  v p = v n (voltages at positive input terminal and negative input terminal are equal to each other)  i p = i n = 0 ( currents entering the positive and negative input terminals are zero ) ipip inin An Ideal Op amp has infinite open-loop gain, infinite input resistance and zero output resistance

EE 1270 Introduction to Electric Circuits Suketu Naik 7 Example 5.1 a) a) Find v o if v a =1 V, v b =0 V

EE 1270 Introduction to Electric Circuits Suketu Naik 8 AP5.1 a) a) Find v o if v s =0.4, 2.0, 3.5, -0.6, -1.6, -2.4 Q: Which values of v s will cause op amp to saturate?

EE 1270 Introduction to Electric Circuits Suketu Naik 9 p5.4 a) & (b) a) Find v o if v a = 1.5 V and v b = 0 V b) Find v o if v a = -0.5 V and v b = 0 V

EE 1270 Introduction to Electric Circuits Suketu Naik 10 Op-Amp Configurations 1) Inverting Amplifier 2) Non-inverting Amplifier 3) Voltage Follower (or buffer) 4) Summing Amplifier 5) Difference Amplifier

EE 1270 Introduction to Electric Circuits Suketu Naik 11 Inverting Amplifier 1) Output and Input signals have opposite polarity (180 ° phase shift) 2) Inverting Amplifier provides negative voltage gain

EE 1270 Introduction to Electric Circuits Suketu Naik 12 Example 5.2: Design of an Inverting Amplifier

EE 1270 Introduction to Electric Circuits Suketu Naik 13 p5.8: Design of an Inverting Amplifier