Hi
We have a project where we have to convert a rectified AC signal which is sitting at 3.5V range to one which is sitting at 0V. So we basically need to have a gain of 1. What kind of circuit would be the best to get the desired result?

Thanks
Namratha

 

Do you mean you want to remove the DC component of the rectified AC?

 

yes, we need to do that.

 

I'll assume you're talking about an ac signal riding on 3.5 volts dc and you want to shift it to an ac signal riding on zero volts dc. You need a double ended supply for this so that the signal can swing between negative and positive voltages.

If the ac signal is not high frequency, say it's an audio signal, then use an op amp. Depending on your need you can amplify the signal or simply shift it's dc voltage level. In the first case use a capacitively coupled inverting or non-inverting configuration; in the second case use a capacitive-coupled follower configuration.

If the output needs to be exactly zero, then use a ten-turn pot as the (or part of the) feedback resistor or sampling resistor; or if you use unity gain, take advantage of the the op amp's offset input to null the output to zero.