differentiator circuit behaviore

[pankaj jha]

hello everyone
can anyone plz explain me the following points regarding the differentiator:
1) The output of a differentiation circuit is often unusable because of input noise. Because the derivative of a signal includes high frequency noise and the output of a differentiator is proportional to its frequency, we have to limit the bandwidth of the circuit.

 

[keith1200rs]

Add a resistor in series with the differentiator capacitor and/or a capacitor across the feedback resistor.

Keith

 

[allanvv]

Ideal differentiation in the frequency domain is multiplying by jw. This is a zero at the origin. The magnitude increases linearly with frequency (log-log), so that means it amplifies high-frequency noise.

 

[LvW]

hello everyone
can anyone plz explain me the following points regarding the differentiator:
1) The output of a differentiation circuit is often unusable because of input noise. Because the derivative of a signal includes high frequency noise and the output of a differentiator is proportional to its frequency, we have to limit the bandwidth of the circuit.

The bandwidth must be limited (applying the methods mentioned by Keith) not because of noise but because of stability reasons.
To understand this you have to study feedback and associated stability issues (Bode diagram, Nyquist criterion).