1. Lecture 8: Op Amps and Circuits Nilsson 5.1-5.6
ENG17: Circuits I
Spring 2015
April 23, 2015

2. Overview Usage Op Amp Overview Fundamental Operation
Basic Op Amp Circuit
Amplifier Circuits

3. Usage: Strain Gauge Measure strain by measuring change in resistance
Problem: hard to measure tiny resistance change
Δ𝑅=2𝑅 Δ𝐿 𝐿

4. How to Measure Measure voltage across Wheatstone bridge
Voltage still a small quantity
…Use an Op Amp to amplify the voltage!
Op Amp = Operational Amplifier
Indicates potential to perform math operations
Indicates potential to amplify input signals

5. Overview Usage Op Amp Overview Fundamental Operation
Basic Op Amp Circuit
Amplifier Circuits

6. Op Amp Terminals

7. Off-note
Bob Widlar
Co-creator (w/David Talbert) of first mass-produced op amps
Also created this advertisement

8. Terminal Voltage / Current
Follows the Node-Voltage Setup
All currents set up as going into the “black box”

9. Overview Usage Op Amp Overview Fundamental Operation
Basic Op Amp Circuit
Amplifier Circuits

10. Voltage Transfer Characteristic
A = gain (multiplying constant)
Use “negative feedback” to stay in linear region

11. Overview Usage Op Amp Overview Fundamental Operation
Basic Op Amp Circuit
Amplifier Circuits

12. Op Amp Circuit

13. Example – Op Amp

14. Overview Usage Op Amp Overview Fundamental Operation
Basic Op Amp Circuit
Amplifier Circuits

15. Inverting Amplifier Circuit

16. Operating “Open Loop”

17. Noninverting Amplifier Circuit

18. Summing Amplifier Circuit

19. Difference Amplifier

20. Example

21. Example