Message	Date	From	Subject
10417	2014-11-05 10:10:00	bob_ledoux	Choosing R and C Values for Active Filters
Active filter theory defines an R and C combination for each pole. We have freedom to chose a value for either R or C and have the other value computed. Typically, we emphasize small R values for low noise. I'm using QuadNet to design a phase delay network for an SSB receiver. Phase delay active networks require very precise component values. I decided to use a 20 turn 1K trimmer to adjust the low frequency supression. For a resistance below 1K a cap of 2uf is called for. That is a big cap. My plan is to measure the cap within 0.1% and then calculate the resistance. What are the short comings of this plan?

Active filter theory defines an R and C combination for each pole. We have freedom to chose a value for either R or C and have the other value computed.

Typically, we emphasize small R values for low noise.

I'm using QuadNet to design a phase delay network for an SSB receiver. Phase delay active networks require very precise component values. I decided to use a 20 turn 1K trimmer to adjust the low frequency supression. For a resistance below 1K a cap of 2uf is called for.

That is a big cap. My plan is to measure the cap within 0.1% and then calculate the resistance.

What are the short comings of this plan?