Engineering Principles V11

Clive W. Humphris


The inverting Op-Amp is the most commonly found configuration. The output has a 180° phase inversion of the input.

Amplifier stage gain is determined by dividing Rf by Rin. Multiply the amplitude of the input by the gain (Av) to find the output amplitude. This can be as peak, peak-to-peak or RMS. value, whichever the input is measured as, even DC levels.

Note the input connection is made to the (-) terminal, signifying it is used as an inverting amplifier. The negative sign of the output voltage also denotes the phase inversion.

Negative signs in electronics do not always mean a negative voltage or current. Usually it's just to show that measurement is opposite to a positive value. For current this would mean it is flowing in the opposite direction.

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