Quote:
Originally Posted by glug
Or is the zener in the MPG circuit going to take care of that?
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More or less. It should clamp the input to around -0.5 volts. A plain rectifier diode between your circuit and the mpguino should clean that up, but might affect low speed sensitivity.
If you're still seeing a sine wave on your circuit output, the amp isn't giving you enough gain. It should be so heavily amplified that the output is swinging from clipping negative to clipping positive with an almost immeasurably steep slope at the crossings. If you were using a single supply op-amp, that would be VCC and ground (or very near it) in response to 0V crossings on your sensor input.