opamp integrator design troubleshooting

[breeze]

hi there,
i've designed a cmos integrator(using an opamp, resistor,and capacitor), but when i put a square wave input, the amplitude of the putput ramp is not uniform. The triangular ramp looks like you've pasted many similar ramps, but the next is lower than the previous. The maximum and minimum point of the whole waveform is positive and negative supply of the opamp. Does the error lie on the choice of capacitor or resistor(I've tried many values.) or somewhere else? Can anyone help me find the error?

 

[FRIED]

If everything is not perfectly balanced, the output of the integrator will drift to one of the rails. This includes the offset of the amp, any DC offset or mark/space of the square wave.

 

[audioguru]

Frequently a high value resistor is connected across the capacitor to stop the voltage drift.

Keep the input level low enough or its frequency high enough so that the opamp's output doesn't hit the rails.