OK, you have an AC voltage, what frequency? This will throw a few caveats into things. Let me think this through and suggest a circuit. What exactly is the signal and what frequency is the signal?

Ron

 

Well, the input sinusoidal signals frequency has to be between 0 - 500kHz with a resolution of 0.1Hz.

 

Hey, I reading online about a ADC0804 converter. Can this be used instead of the LM339?

 

What you want since you have an AC signal is a comparator circuit designed for AC signals. Using this link scroll down to some of the AC VOLTAGE-ACTIVATED CIRCUITS. I wrongly assumed a 3.3 volt DC you wanted to monitor. I do not see an ADC as viable but I never tried it with an AC signal.

Ron

 

What you want since you have an AC signal is a comparator circuit designed for AC signals. Using this link scroll down to some of the AC VOLTAGE-ACTIVATED CIRCUITS. I wrongly assumed a 3.3 volt DC you wanted to monitor. I do not see an ADC as viable but I never tried it with an AC signal.

Ron

Okay, thanks for the help