Size of passives for active filter


I am working with the CS42436 codec, and in their datasheet, they have recommended values for components to be used in an active filter that takes the differential outputs from the DACs and converts them to a single-ended channel.

I have no problem with the values and what components to use, although I am concerned about the power going through the resistors and such. Right now, I am using the recommended design using 0402 resistors and capacitors. Apart from the assembly, will this size be okay for an active filter or do I need bigger components that can handle higher power?

Current design with 0402 components

Best Answer

0402 resistors might be rated for either 1/10 W or 1/16 W. You'll have to check the specs of the parts you're actually using (or, if you're buying off EBay or something, just assume 1/16 W).

Then you'll have to calculate for each one in the circuit, how much power it is consuming. For an analog filter, you want to consider the maximum input amplitude case.

If the power consumed is less than 0.5 or 0.75 of the rating, you are probably okay with 0402. If you power consumed is more than that, use a bigger part. You might even want to limit the consumed power to less than 0.5 of the rating to avoid self-heating causing your filter characteristics to drift, depending how repeatable you need the filter's performance to be.