Summing Differentiator Circuit:

Similar to the summing integrator, summing can be obtained using the basic differentiator Circuit. It can be obtained by applying more than one input to the basic Summing Differentiator Circuit as shown in the Fig. 2.50.

Summing Differentiator Circuit

The node B is grounded, hence potential of A is also zero. So VA = 0. Hence we can write the expressions for the various currents as,

and

Summing Differentiator Circuit

Applying at node A,

Taking of the Equation,

Summing Differentiator Circuit

where

and

Summing Differentiator Circuit

i.e.

As RC1 is very much higher than R1C1 and R2 C2, we get,

Summing Differentiator Circuit

Replacing s by d/dt,

For C1 = C2 we get,

Summing Differentiator CircuitThe expression shows that the output is the sum of the differentiations of the two inputs. Hence the circuit is called as Summing Differentiator.

The resistance R1 is introduced to provide closed loop stability at high frequency and to reduce the high frequency noise.