[SOLVED] Low Pass Filter Design using only mosfets

[tailsmp]

Hey guys,

I need to design a low pass filter using only mosfets, i am not allowed to use any op-amps. All I need is a basic circuit schematic for low pass filter using only mosfets. Thank you, please help.

PS. I searched the forum but nobody has asked a simple question like mine, all the filter related topics are complex than my problem .

 

[FvM]

The question isn't really clear. I tend to understand active filters with MOSFET amplifiers.

That's basically possible. I can imagine e.g. Sallen-Key filters with MOSFET source followers as buffer. To turn the post in a meaningful question, you would want to mention a filter specification.

Needless to say that you can also design passive filters without any semiconductor components.

 

[tailsmp]

Yeah, question is to design an active low pass filter with MOSFET amplifiers. To be specific my filter must have

-Cutoff Frequency at 900khz
-Gain must be 20dB or higher
-The design could only have MOSFETs or BJTs, (i.e. I can use CA4056 array but not UA741 Op-Amp.)

Sorry for not being clear before.

 

[FvM]

Still not a complete specification.

Particularly I don't see what the gain specification has to do with the low-pass filter itself. It just says there should be an additional amplifier stage, e.g. in common source configuration.

 

[crutschow]

Check this thread.

 

[tailsmp]

Thank you crutschow and FvM for your help. I am an engineer student who is just taking the Analog Electronics Course for the first time because of that I had problems explaining my situation. Anyway thanks

 

[LvW]

Hi tailsmp,

attached you will find a second order lowpass in Sallen-Key topology using two BJT´s. Perhaps it helps to find a solution for your problem.
I do not have any parts values - perhaps circuit simulation can help to find suitable values.