I am designing a basic 100kHz active bandpass filter using opamps (LF353). I am only interested in receiving the 100kHz frequency (might drift a few kHz) from my input signal. I have used a basic Fliege bandpass filter, because it has low component count, simple, uses only 2 opamps and has adjustable frequency and Q control.

V(in) = 2v(p-p) sine wave 100kHz (for testing)
Bandwidth: 20kHz
f1 = 90kHz
f2 = 110kHz

Any suggestions for improvement or new designs?
I have no restrictions except that I would like to use no more than 2 opamps, preferably LF353.

This is my design: Circuit diagram - Fliege filter - band pass

And the Bode plot: Bode plot

  • \$\begingroup\$ It seems to have the same number of components as a Sallen Key bandpass filter circuit would have (8). Both designs use only a single dual opamp package IC, which your LF353 will do. Check out some nice designs here: eng.yale.edu/ee-labs/morse/compo/sloa058.pdf \$\endgroup\$ – KyranF Mar 31 '14 at 10:13
  • \$\begingroup\$ A "Twin-T filter" with active feedback can allow adjustments to Q, for potentially better selectivity than Sallen-Key 2nd order filter. \$\endgroup\$ – Brian Drummond Mar 31 '14 at 10:50
  • \$\begingroup\$ I have designed a Sallen Key filter (2 opamps) and the frequency response obtained seems a little poorer in comparison with the Fliege filter above. Also, the Fliege filter seems to be more adjustable in terms of frequency. However, I will look into that pdf document. \$\endgroup\$ – nesslersreagent Apr 1 '14 at 13:50
  • \$\begingroup\$ The "Twin-T filter" sounds interesting. But, I'm more keen on frequency adjustment as opposed to quality factor. Nonetheless, I will look into it. \$\endgroup\$ – nesslersreagent Apr 1 '14 at 13:52

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