[sdiy] SSM2164 state variable filter

[Neil Johnson]

Hi,

David G. Dixon wrote:
> Zeners across the first integrator cap work perfectly and are very  
> simple.
> As far as the designer in me is concerned, this case is closed.


Trouble with that approach is that at low frequencies the current  
output from the 2164 gain cell is pretty small.  At this level the  
leakage current through the back-to-back zeners becomes important,  
and in effect you have a leaky integrator.
That's why in my filter design the limiting zeners are not across any  
of the integrator caps, but sit on the LPF feedback path.

Cheers,
Neil
--
http://www.njohnson.co.uk