User Tools

Site Tools


instramp:dcfilter
C1 (DC filter)

Now, we add C1 which decouples the 1st and 2nd stage amplifier. It filters out any DC from from by the instrumentation amplifier. Otherwise the gain of 100 of the OP-amp would amplify the DC further and would drive it into saturation. The cutoff frequency is at f=1/(2 pi RC)=0.2Hz but note that it's a first order highpass so that the transition is very wide.

Note that the value of 1uF is OK for EMG (muscle activity) but for ECG (heart) and EEG (brain wave) a capacitor of 4.7uF is recommended (because it's just 1st order).

next step: Ground connections

instramp/dcfilter.txt · Last modified: 2014/05/03 01:33 by berndporr