I want to be able to safely convert any voltages above a threshold voltage of +-1V with a maximum voltage level of +-20V to the logic level (3.3V). I ended up using an op-amp to construct a Schmitt trigger with the resistors and the power supply for the high threshold voltage of ~1V and the lower threshold voltage of ~0.5V. The circuit is shown below
Upon building this circuit using a LF353N op-amp and testing it out, I found that the output of the circuit just hits a DC level of about 3V when the input passes a voltage of 6V peak-peak. I also found that the waveform it produced was has curves on the top looking a bit like this:
The frequency of the waves I'm dealing with are around 10kHz - 100kHz and I was wondering if these effects are due to the fact that the slew rate of the LF353N is too slow?