Problem with the integrator circuit

Hi

I am trying simple integrator circuit with cadence using op-amp from its generic analog library (ahdl lib). This simple design works fine with sine input that I get nice cosine output.

But feeding it with a pulse source doesn't result in an expected triangular wave.
Does anyone see anything wrong. The circuit and the wave scan is appended.
Later I will implement SC integrator.

Pls help.

The circuit implements a low-pass rather than an integrator, it won't generate a triangular wave anyway.
But you should show the input waveform for clarity. Also it's not clear, if the OP is suited for single supply operation.

warlock_ajay said:

Hi

I am trying simple integrator circuit with cadence using op-amp from its generic analog library (ahdl lib). This simple design works fine with sine input that I get nice cosine output.

But feeding it with a pulse source doesn't result in an expected triangular wave.
Does anyone see anything wrong. The circuit and the wave scan is appended.
Later I will implement SC integrator.

Pls help.

Click to expand...

You cannot implement an analog "ideal" integrator. This would imply an amplifier with really infinite gain. Thus, you only can choose an active lowpass with a corner frequency (pole) as low as possible. However, this approach is limited by offset properties of the opamp.
Compromize: Lowpass with a pole frequency at least 50...100 times lower than the wanted integration time constant (which is identical to the invers of the angular frequency which leads to a gain of unity.)

Added after 18 minutes:

But be careful: The dc gain of the opamp (with feedback) shouldn't be above app. 1E3 (because of offset).
Hint 1: Usage of an OTA wouldn't help too much, since it is not an ideal current source (this is a common misunderstanding).

Hint 2: In case you are going to use the integrator within an overall dc stabilizing feedback loop, no resistor across the integration cap is necessary!.