RC filter component selection

[Mark Whitney]

for example if i added a 500nF capacitor in parallel with that 100pf one ( easier than swapping, its a 603 smt component) i should (if my studying has paid off) get a lowpass of 3.18khz there, instead of the current 15mhz one.

A problem with using 100 Ohm / 500nF is the low impedance at higher frequencies. This could be a problem for the opamp connected as the source.

 

[robinlawrie]

A problem with using 100 Ohm / 500nF is the low impedance at higher frequencies. This could be a problem for the opamp connected as the source.

Yeah i thought that might be the case.

I assume adding a resistor in series with the capacitor to raise impedance at the high frequencies, without affecting impedance at lower ones is a "thing" probably well known and with a name.

I assume it would reduce effectiveness of filter, and depend on ratio between resistor chosen, and input impedance of next stage of amp...?

 

[PRR]

for example if i added a 500nF capacitor in parallel with that 100pf one......

I say try it.

Cap loading is not an issue here.