Alternating circuits are widely using in electronics. The voltage can be increased or decreased using a transformer, and the resulting voltage will have the same general shape as the original voltage. An operational amplifier will amplifier the voltage, but the output will be a more nearly square wave than the alternating input.
Suppose an voltage is applied to the input Q above. A fraction of the output voltage,
is fed back into the op – amp at P in a negative feedback loop.
Using the op – amp equation
and
we have
(1)
The closed loop gain
is
and we can substitute this into (1) to obtain
Usually
so
Hence for a non inverting amplifier, the closed loop gain