Adjustable Active Filter

Discussion in 'The Projects Forum' started by Crowbar, Jan 4, 2007.

  1. Crowbar

    Thread Starter Active Member

    Dec 19, 2006
    Hi, Have a second-order Sallen-Key low-pass Butterworth Filter. Cutoff frequency must be adjusted: 10Hz, 100Hz, 1000Hz. The reasonable way for me is to use switching capicitors and resistors- will be there any problems if switching will be done with Analog Switch(like MAX333 etc) in contrast to simple toggle/rotary switches?
  2. Ron H

    AAC Fanatic!

    Apr 14, 2005
    I would make 3 separate filters, with a 3 pole, single-throw switch (analog or rotary), followed, if necessary, by a voltage follower. This gets around any potential problems with switch resistance and capacitance. You use fewer switches and more op amps.