RE: Blog 2: As much as Polymer Capacitors can go in Instrumentation Amplifier.

michaelkellett — Tue, 04 Jun 2019 08:14:39 GMT

You might like to consider what useful purpose C1 has in this circuit and with the values you have chosen for C1, C2 and C3 and R1 and R2.

Because C2 and C3 are both connected to ground their series value shunts C1 - so why not remove C1 completely and increase the value of C2 and C3 to keep the impedances the same.

Alternatively increase R1 and R2 and keep C2 and C3 = 4.7uF to keep the filter response the same.

Now you can do your test without using a huge MLCC.

I must point out that this is not a rational way to test these capacitors - the 4.7uF POSCAPs have a claimed ESR of 0.3R and you have series resistors in your design of 10R -

so a change in cap ESR of 100% will make a difference of about 3% to the cut off frequency of the filter, but the tolerance on capacitor value is 20% and will swamp this small effect.