How can I design a notch filter using only GM-C OTA?

[mike009]

Hello,
How can I design a notch filter using only gm-C OTA? I want to filter the 50 Hz frequency from a 250 Hz bandwidth, with a notch filter, something like twin-T. My question is how do I design the schematic only with Gm and C.
Thank you, community

 

[LvW]

Re: Gm-C Notch filter

Hello,
How can I design a notch filter using only gm-C OTA? I want to filter the 50 Hz frequency from a 250 Hz bandwidth, with a notch filter, something like twin-T. My question is how do I design the schematic only with Gm and C.
Thank you, community

I am afraid twin-T will not work with OTA´s (and is also for opamps not recommended).

Instead, using two or three gm stages you can realize notches with "universal filter" structures. Examples are given with Fig. 7 of the following pdf file:

**broken link removed**