Microelectronic Circuits Chapter 9. Operational Amplifiers EE141 Microelectronic Circuits Chapter 9. Operational Amplifiers School of Computer Science and Engineering Pusan National University Jeong Goo Kim

9-1 Introduction Operational Amplifier(op amp) One of the basic building blocks for constructing analog systems Used for a variety of purposes A voltage amplifier with an extremely high voltage gain An ideal linear voltage amplifier Differential amplifier : vin is voltage difference between two input

9-2 Ideal Op Amp Ideal op amp Noninverting terminal, i+, v+ Infinite input resistance Ri=∞ Open loop gain Av→ ∞ Vo = Av(v+ - v- ) i+ = i- = 0

Ideal op amp with real voltage supply limits Negative feedback a large class of useful circuits with op amps. closed-loop gain, AF Ideal op amp with real voltage supply limits output voltage cannot exceed the supply voltage

9-3 Noninverting Amplifier feedback to the noninverting input input voltage negative feedback causes no current flows into input, therefore closed-loop voltage gain Example 9.1

9-4 Unity-gain Buffer Unity-gain buffer output voltage is same as input voltage input voltage closed-loop gain

9-5 Inverting Amp Inverting amp Example 9.2 9-5 Inverting Amplifier 9-5 Inverting Amp Inverting amp feedback to the inverting input negative feedback causes current through R1 current through R2 closed-loop gain Example 9.2

9-6 Principle of Negative Feedback The op amp differential amp gain is extremely high output voltage stabilizes at a value that exactly feeds back the proper voltage level to place Drill Exercise

9-7 Differential Amp Differential Amp CMRR voltage current output vol. Common Mode Rejection Ratio how nearly ideal a diff amp is.

9-7 Differential Amp Drill Exercise ans:

9-8 Summing Circuit 9-8 Summing Circuit current KCL output vol.

9-9 Integrator current combining output vol. Example 9.3

9-10 Active Filter complex voltage gain here and therefore half-power point

9-11 Current-to-Voltage Converter transresistance Example 9.4

9-12 Nonideal Op Amp Real limitation of the op amp Output voltage is limited by power supply voltage(s) Finite gain Limited frequency response Finite input resistance Finite output resistance Finite slew rate Input bias current Input bias current offset Input offset voltage Finite common mode rejection ratio (CMRR)

feedback current inverting voltage output voltage voltage gain 9-12 Nonideal Op Amp feedback current inverting voltage output voltage voltage gain

Chapter 10. Semiconductors, Diodes, and Power Supplies Homework EE141 Homework Read textbook pp. 354-394 Solve problems 9.1, 9.7, 9.14, 9.20, 9.27, 9.31, 9.35, 9.46 Next Lecture Chapter 10. Semiconductors, Diodes, and Power Supplies