I am looking at using the OP1177 to act as an active low pass filter. I need to smooth out a 20kHz signal burst with a minimum of 50 cycles to reach a voltage on the output to interrupt an microcontroller.
However when I use the op-amp I get a very big offset voltage at the input. I have a gain of ten but I get a minimum input voltage of ~160mV. The input offset voltage of the op-amp is 60uV maximum so it can't be that. Does anyone have any idea what parameter or method of analysis I should be looking out to defeat this problem? I am going to change to a LT1001 op-amp which runs without this problem in simulations but any ideas would be greatly appreciated!