1. EE 1270 Introduction to Electric Circuits Suketu Naik 0 EE 1270: Introduction to Electric Circuits Lecture 13: Operational Amplifiers Part 2 Chapter 5 The Operational Amplifiers Sections 5.4-5.7

2. EE 1270 Introduction to Electric Circuits Suketu Naik 1 Operational Amplifiers Pin Diagram Positive Power Supply Negative Power Supply

3. EE 1270 Introduction to Electric Circuits Suketu Naik 2 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

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

5. EE 1270 Introduction to Electric Circuits Suketu Naik 4 Non-inverting Amplifier 1) Output and Input signals have same polarity (0 ° phase shift) 2) Non-inverting Amplifier provides positive voltage gain

6. EE 1270 Introduction to Electric Circuits Suketu Naik 5 AP 5.4 a) Find the output voltage when R x =60 kΩ b) How large can R x be before saturation

7. EE 1270 Introduction to Electric Circuits Suketu Naik 6 Voltage Follower (Buffer) Q: Why use voltage follower (Gain=1)?  Suppose R g =R f =0 (short), R s =Inifinite (open)  Circuit becomes voltage follower, e.g. v o =v i

8. EE 1270 Introduction to Electric Circuits Suketu Naik 7 Summing Amplifier A Summing Amplifier combines several inputs and outputs the weighted sum of the inputs

9. EE 1270 Introduction to Electric Circuits Suketu Naik 8 Summing Amplifier: Application Digital to Analog Converter (DAC) Q: Why do we use DAC?

10. EE 1270 Introduction to Electric Circuits Suketu Naik 9 p5.17: Design of a Summing Amp Design the Summing Amplifier so that VaVa VbVb VcVc VdVd RaRa RbRb RcRc RdRd

11. EE 1270 Introduction to Electric Circuits Suketu Naik 10 Difference (Differential) Amplifier A Difference (Differential) Amplifier amplifies the difference between two input signals but rejects signals common to the inputs Differential Amp rejects Common-mode signal (noise or DC) If R a /R b =R c /R d (same ratio) then...

12. EE 1270 Introduction to Electric Circuits Suketu Naik 11 Differential Amplifier: Application Instrumentation Amplifer (IA) An Instrumentation Amplifier (IA) is used for precise measurement and amplification with noise reduction in sensors and data acquisition systems

13. EE 1270 Introduction to Electric Circuits Suketu Naik 12 AP5.5a: Differential Amplifier Find range of V a that results in linear operation (avoids saturation) Use Eq (5.22) (because R a /R b ≠ R c /R d )

14. EE 1270 Introduction to Electric Circuits Suketu Naik 13 p5.29: Design of a Differential Amplifier Find range of V a that results in linear operation (avoids saturation) Use Eq (5.22) (because R a /R b ≠ R c /R d )