Q. Draw and explain a differential circuit

A differentiator is a high pass RC circuit having a very small time constant. It is a circuit which gives an output voltage proportional to the derivative of the input voltage. A high pass RC circuit is a circuit, which allows only high frequency to pass through.

               The output current         I = C dVi/dt.

∴ V out= Rcdvi/dt

∴Vo ∝ d (vi)/dt

For a high pass RC circuit to act as differentiator time constant (t) of the circuit (RC) should be very much less than the input time period (T). Here if we give a constant input we get no output. For sine wave as input we get cosine wave as output. For square wave we get narrow pulses as output.