Op-amps: the inverting amplifier
Simulate an op-amp amplifier with power supplies and verify the gain.
An op-amp with negative feedback has a gain set only by resistors. For the inverting amplifier the gain is -Rf / Rin.
- Open the Component dialog, find the Opamps folder and place UniversalOpamp2 (or a real part such as LT1001).
- Connect the non-inverting input (+) to ground.
- Place Rin (1k) from the signal source to the inverting input (-), and Rf (10k) from the output back to the inverting input (-).
- Add two DC sources of +15 V and -15 V to the op-amp supply pins and ground their other ends.
- Use SINE(0 0.5 1k) as the input and run .tran 5m.
A 0.5 V peak input should give a 5 V peak output, inverted. Now raise the input to 2 V peak: the output clips near the supply rails because the op-amp cannot swing beyond them.
If the output sits stuck at a rail, check the supply connections and that feedback goes to the inverting (-) input.