summing amplifier configuration (A-level only) Flashcards – AQA A-level Physics (7408)

What does a difference amplifier do, and what components does it use?

It uses an operational amplifier and a matched resistor network to produce an output proportional to the difference between two input voltages.

For a matched difference amplifier, what is the output voltage in terms of non-inverting input $V_+$, inverting input $V_-$, feedback resistance $R_{\mathrm{f}}$ and input resistance $R_l$?

$V_{\mathrm{out}}=(V_+-V_-)\frac{R_{\mathrm{f}}}{R_l}$

What is the ideal output of a difference amplifier when its two input signals are equal?

Zero.

What happens to a difference amplifier’s output polarity when the larger and smaller input signals are reversed?

The output polarity reverses.