Differentiator using Operational Amplifier

From the series of operational amplifier articles, today will see about differentiating using operational amplifier.

Of these differentiating concepts, we use Resistor in the feedback path and capacitor as the input element, fed to the inverting input of the operational amplifier.

It leads to the time differentiation of the input signal. The circuit needed for differentiating using op-amp is shown below

 differentiator using op amp


To know how this actually works, we need to feed positive going ramp voltage to the inverting input of the op-amp. In this case the voltage across the capacitor is equal to the Vin at all times. Because the inverting input has virtual ground.

We can observe that the Vout is positive going ramp when Vin in negative going ramp and Vout is negative going ramp when Vin is positive going ramp.


This is due to the fact that the positive going ramp on the input fed to capacitor and constant current through the feedback resistor which is again fed to the capacitor makes the output voltage go negative ramp, because actually the capacitor is discharging, which eventually ends up with the negative ramp voltage on the Vout of the operational amplifier.

Even if it has only limited applications we just formulate using these concepts like

Input Output
Square Wave Spikes (like ECG graph)
Triangular Wave Rectangular Wave
Sine Wave Cosine Wave

So today we have covered up the differentiator concept of op-amp, will meet up with remaining concept of operational amplifiers in the coming days.

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Author: JAY

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