1. 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

2. 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

3. 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

4. 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

5. 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

6. 9-4 Unity-gain Buffer Unity-gain buffer
output voltage is same as input voltage
input voltage
closed-loop gain

7. 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

8. 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. 9-7 Differential Amp Differential Amp CMRR voltage current output vol.
Common Mode Rejection Ratio
how nearly ideal a diff amp is.

10. 9-7 Differential Amp
Drill Exercise
ans:

11. 9-8 Summing Circuit
9-8 Summing Circuit
current
KCL
output vol.

12. 9-9 Integrator current combining output vol. Example 9.3

13. 9-10 Active Filter complex voltage gain here and therefore
half-power point

14. 9-11 Current-to-Voltage Converter
transresistance
Example 9.4

15. 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)

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

17. Chapter 10. Semiconductors, Diodes, and Power Supplies
Homework
EE141
Homework
Read textbook pp
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