On Sun, Jan 30, 2011 at 8:59 AM, Olin Lathrop wr= ote: > V G wrote: > > Schematic: http://img411.imageshack.us/img411/997/schematic1.png > > > > The AD620 functions as the differential amplifier and outputs a > > signal into the middle section which acts as a low pass and high pass > > filter. > > It does, but at the wrong frequencies. Your low pass is a 110mHz, and th= e > high pass at 50mHz. I would make the total impedence lower. The input > impedence of the LM324 is not so great. It would also flip the order of > the > two filters, then have the low pass resistor be about 10x the high pass > resistor, which caps sized to suite. > > Q1. What frequencies would you suggest for a bandpass filter? Q2. I'm looking into just using an active filter IC instead of RC filters. Would that be a better idea? 3. I am also using new ICs. the instrumentation amplifier is now an LT1168 and the opamp is an LTC1050. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .