I'm sending in a sine wave with an A = 120mVpp, f = 200 Hz into a http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/opampvar5.html" [Broken] to invert the signals into the positive range. After some circuitry to work with the signal after I've applied the sine wave + offset, at the end I want to remove the DC offset to interface it to a DSP chip. I can't really get into specifics, since it's for my employer, but as of right now I have a high-pass RC circuit setup. My problem is that when I send in a 120mVpp sine wave, I get a 160mVpp sine wave as the output, without the DC offset. I'm trying to be as accurate as possible. I'm using metal film resistors that have 1% tolerance and LM324 op-amps (with +/- 15V). C_highpassfilter = .1uF, ceramic. R_highpassfilter = 1Meg. Anybody know the problem?