DC offset voltage measurement

[sahko123]

for an amplifier im designing i want to know the dc offset on a signal as a 1:1 output voltage (a circuit that outputs the dc offset voltage without the signal). My idea was to have a differential amplifier set up as a buffer on either side of an ac coupling capacitor. Would this make sense as an applicable circuit? or are there better ways of getting the desired result?

[David Hess]

I think you mean an instrumentation amplifier and not a differential amplifier

What you suggest can work and is common with DC servo circuits which correct DC offset of an amplifier.  RC lowpass filters are applied to the input and output and then an amplifier measures the resulting DC difference.  Typically a low input bias current amplifier is used so that the filter time constants can be as long as possible with reasonable values of resistance and capacitance.

[sahko123]

when i said differential amplifier i meant that ill have something at either end of an rc highpass filter (at a frequency beyond what i need like 30khz or something arbitrary) that measures the difference between the voltages at either end of the capcitor

[Zero999]

You need a low pass filter to get the DC offset. It's not clear what you're talking about. Please post a schematic.

[sahko123]

Because of how low the frequency of the signal is (audio 10hz to 20khz) i would need an ac coupler the basic circuit concept is as pictured. As far as i know its essentially performing common mode rejection to get the dc bias.