4th order lowpass with one transistor

[AudioAngel]

Hello,

I've read on a magazine that it is possible to build a 4th order lowpass only by using on transistor stage instead of cascading two 2nd order stages. Is that true? Can anyone guide me, how to do that?

Regards,

Raphael

 

[myhrrhleine]

Hi,
A 4th order filter does not require *any* transistors/amplifiers/buffers but
the response of amplitude vs. frequency may be less than desirable for your application.

To answer your question fully, one would have to know something about the desired response curve.

 

[AudioAngel]

Ok, for an example let's say we want to make a Bessel filter with the design frequency 1kHz.