Transcript Lecture 8: Op Amps and CircuitsNilsson 5.1-5.6

Lecture 8: Op Amps and Circuits
Nilsson 5.1-5.6
ENG17: Circuits I
Spring 2015
April 23, 2015
1
Overview
• Usage
• Op Amp Overview
• Fundamental
Operation
• Basic Op Amp Circuit
• Amplifier Circuits
2
Usage: Strain Gauge
• Measure strain by measuring change in
resistance
Δ𝑅 = 2𝑅
Δ𝐿
𝐿
• Problem: hard to measure tiny resistance
change
3
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
4
Overview
• Usage
• Op Amp Overview
• Fundamental
Operation
• Basic Op Amp Circuit
• Amplifier Circuits
5
Op Amp Terminals
6
Off-note
Bob Widlar
Co-creator (w/David Talbert) of first
mass-produced op amps
Also created this advertisement
7
Terminal Voltage / Current
Follows the Node-Voltage Setup
All currents set up as going into
the “black box”
8
Overview
• Usage
• Op Amp Overview
• Fundamental
Operation
• Basic Op Amp Circuit
• Amplifier Circuits
9
Voltage Transfer Characteristic
A = gain (multiplying constant)
Use “negative feedback” to stay in linear region
10
Overview
• Usage
• Op Amp Overview
• Fundamental
Operation
• Basic Op Amp Circuit
• Amplifier Circuits
11
Op Amp Circuit
12
Example – Op Amp
13
Overview
• Usage
• Op Amp Overview
• Fundamental
Operation
• Basic Op Amp Circuit
• Amplifier Circuits
14
Inverting Amplifier Circuit
15
Operating “Open Loop”
16
Noninverting Amplifier Circuit
17
Summing Amplifier Circuit
18
Difference Amplifier
19
Example
20
Example
21