Applications of Operational Amplifiers: Differentator

Differentator:

A circuit in which the output voltage waveform is the diffe­rentiation of input voltage is called differentiator.as shown in fig. 1.

Fig. 1

The expression for the output voltage can be obtained from the Kirchoff's current equation written at node v₂.

Thus the output vo is equal to the RC times the negative instantaneous rate of change of the input voltage vin with time. A cosine wave input produces sine output. fig. 1 also shows the output waveform for different input voltages. The input signal will be differentiated properly if the time period T of the input signal is larger than or equal to Rf C. T ³ Rf C As the frequency changes, the gain changes. Also at higher frequen­cies the circuit is highly susceptible at high frequency noise and noise gets amplified. Both the high frequency noise and problem can be corrected by additing, few components. as shown in fig. 2.

Fig. 2