Hi, I was wondering if anyone knew how to design a single supply difference amplifier... I don't want a comparator or a difference amplifier chip. I need something that will output an AC wave. The inputs of the amplifier are AC sine waves which have slight difference in amplitudes. I designed one using a schematic I found on Google but I need one that is single supply. When I try to put a DC bias and make the op-amp I'm using a single supply the output is an AC wave but it doesn't seem to work correctly. The output from the amplifier is going into a synchronous demodulator, so I’m also using a DC Blocking Capacitor at the output of the amplifier. I did to use both a very small cap and a relatively small cap and both didn’t work. I’m putting the cap at the end of the amplifier because I want to block any DC bias. Any help is greatly appreciated!