A circuit in which the output voltage waveform is the integral of the input voltage waveform is called integrator. Figure 1, shows an integrator circuit using OP-AMP.
Figure 1
Here, the feedback element is a capacitor. The current drawn by OP-AMP is zero and also the V2 is virtually grounded.
Therefore, i1 = if and V2 = V1 = 0
Integrating both sides with respect to time from 0 to t, we get
The output voltage is directly proportional to the negative integral of the input voltage and inversely proportional to the time constant RC.
If the input is a sine wave the output will be cosine wave. If the input is a square wave, the output will be a triangular wave. For accurate integration, the time period of the input signal T must be longer than or equal to RC.
Figure 2, shows the output of integrator for square and sinusoidal inputs.
Figure 2
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