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In the LM311 circuit below that is used as a comparator, how does voltage at the reference (- Input), affect the output?
For a sine wave, would having a higher voltage at the reference increase or decrease the duty cycle of the output?
And finally, is there a way to calculate this duty cycle, based on the resistor values of the voltage divider at the reference input?
NOTE: The circuit above is just for reference. The application I am using an LM311 for is something else.
The comparator output will change states based upon when the signal voltage at the + input goes above or below the reference voltage on the - input. Selecting the reference voltage has everything to do with the nature of the input signal levels. The sample circuit you show sets the reference at 2.5 volts. So you would expect the output to reflect a high whenever the input signal voltage is above 2.5V and low when the signal voltage is below 2.5V.
From this explanation you should be able to extrapolate the behavior of the comparator if you adjust the reference relative to a known input signal.
Do be aware that the comparator will have a valid operating voltage range for its inputs so do be aware of this as you go about changing the voltage on the reference and the input signal pin.
