PHYS245 Electricity and Electronics
Syllabus - Classes - Assignments - Laboratory - Resources
Class 35: Operational Amplifiers

Op Amps
What's inside? 741, LF356

What matters to us:
Generic Op Amp

Golden Rules of Op Amps

  1. With negative feedback, the output attempts to do whatever is necessary to make the voltage difference between the two inputs ZERO.
  2. The inputs draw no current.

Inverting Amplifier
Inverting Amplifier
gain = - Rf / Ri

Non-Inverting Amplifier
Non-Inverting Amplifier

gain = 1 + Rf / Rg

Voltage Follower
Voltage Follower

gain = 1, but presents extremely high input impedance (that of the op amp input) and low output impedance.

Watson's rule III: Don't be afraid to use another op amp.

Quiz 7: Amplifiers and Analog Signals

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Last updated May 7, 2005.
Copyright George Watson, Univ. of Delaware, 2005.