BartlebyScrivener
Member level 5
I have tried to design a third order active filter with a cut off freq of 20kHz. Using 10 kOhm resistors, I make that the capacitors should be 795pF using 2*pi*f = 1/CR
I made a folded cascode amplifier, with an output buffer stage
then added a first order filter to the output
then added the first order to the input, and the cap to the output.
But I seem to get a first order response when I do an ac sweep? Also, the -3dB point is around 1kHz instead of 20kHz.
What am I doing wrong?! Thanks.
I made a folded cascode amplifier, with an output buffer stage
then added a first order filter to the output
then added the first order to the input, and the cap to the output.
But I seem to get a first order response when I do an ac sweep? Also, the -3dB point is around 1kHz instead of 20kHz.
What am I doing wrong?! Thanks.
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