[sdiy] SSM2164 Filter Cells

[Jay Schwichtenberg]

Scott,

I was thinking of generic filter cells like the SSM2040, CEM3320 and LM13X00
use. There they have a cap between the filter cell and current amp. The
other end of the cap can be connected to ground for a low pass and all pass
filter and used as an input for high and all pass filters. Refer to figs 11
& 12 of the LM13700 data sheet that will show you the low and high pass
configurations. All the SSM2164 designs I've seen have a cap in a feedback
loop of an op-amp. I view a cap in a feedback loop as an integrator which
should be linear and a cap between ground and a signal just charging a cap
which is non-linear. There is a more or less linear range when charging a
cap which is used in a lot of VCOs.

I think that other posts in this thread have enlightened me with the fact
that the SSM2164 likes to drive virtual ground and has a very low voltage
output.

No worries, just need to haul out the Active Filter Cookbook, Art of
Electronics and Electronotes and do some research.

Jay S.

> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl
> [mailto:synth-diy-bounces at dropmix.xs4all.nl]On Behalf Of Scott Nordlund
> Sent: Tuesday, July 21, 2009 7:40 PM
> To: synth-diy at dropmix.xs4all.nl
> Subject: RE: [sdiy] SSM2164 Filter Cells
>
>
>
> > So far I've only seen integrator based filters for the 2164,
> nothing like
> > the regular OTAs (cap between OTA output and output current amp). Anyone
> > know why this is, are there issues with 2164 in this configuration?
>
> I may be missing something here but I don't know of any OTA-based
> VCF that isn't made using integrators.  Do you have an example?
>
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