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What kind of AF LPF is this?

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It is a unity-gain Sallen-Key lowpass topology.
 
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    neazoi

    neazoi

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Hi,

if you need exact cutoff frequency and/or special filter characteristc (Bessel, butterworth...) then if you combine second order to higher order .. each stage has it´s own parameters.
--> two equal lowpass filters, each with Fc of 1kHz will result in a filter with fc smaller than 1kHz.


Klaus
 
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    neazoi

    neazoi

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KlausST said:
Hi,

if you need exact cutoff frequency and/or special filter characteristc (Bessel, butterworth...) then if you combine second order to higher order .. each stage has it´s own parameters.
--> two equal lowpass filters, each with Fc of 1kHz will result in a filter with fc smaller than 1kHz.


Klaus
Click to expand...

I have done that with the second part of the circuit (CW) shown in the picture. I have cascaded 3 of them and I achieved a sharp CW BPF. But this was because this was a bpf and all sections center frequencies were the same and the roll-off just went steeper when cascaded 3 of them.

But in the case of the SSB LPF, how do you propose to do it in a discrete active way?
 

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