Op Amp as an integrator

Op-amp as an integrator:

In the last article we have seen the op-amp comparator. Now we are going to learn another application of operational amplifier as integrator.

Integrator is a circuit whose output is proportional with the area of the input waveform. Following figure shows the op-amp as integrator circuit. We know that the RC circuit itself acts as a simple integrator. But in such circuits the output waveform is not exactly linear triangular waveform as it should be. In op-amp integrating circuit the inverting terminal is virtual grounded by the differential op-amp input circuit as shown in figure. Input current is equal to Vin/R1. As the input impedance of the op-amp is infinite all of I1 will flow to the capacitor.

op amp as an integrator

Working of op-amp integrator:

Let us consider R1 is kept constant. Assume that the input voltage (Vin) is kept constant for a given period of time, hence the value of the I1 is also constant. Because of high impedance all of I1 flows through capacitor so that capacitor starts charging by a constant current source. When input voltage (Vin) is kept constant, the capacitor will charge and discharge at linear rate. The output of this op-amp integrator is shown below.

op amp integrator output waveforms

From the above output waveforms we can observed that when input voltage goes positive (from –V to +V) the output is a negative ramp. Similarly when the input goes negative (from +V to -V) the output is a positive ramp. This implies that the op-amp integrator output is 180 degree out of phase with the input.

We will see another application of operational amplifier i.e. op-amp audio amplifier in the next article.

Pin configuration of Op Amp:

op amp pin diagram