[sdiy] Equiv of LM3900?

[René Schmitz]

At 12:02 02.03.02 -0800, you wrote:
>    Speaking of LM3900's, I have always wanted to try one of the filters
that uses
>a pair of transistors (connected differentially) with a current control to
control
>the cutoff frequency (I think this is refered to as the Arp Filter).  Just
how
>well (both electronically ad soundwise) does this really work?

I've breadboarded such a filter once, I made a SVF. This makes a nice
little filter out 
of a couple of cheap parts, if you go with standard transistors. Though it
didn't impress 
me enough to make a permanent circuit out of it. Maybe I should try the
four pole. 
Its interesting to note that the diff-pair connected to the LM3900 input
mirror 
is a simple OTA structure. Infact the same as used in the SSM2040. Though
the integrator 
is very different. 

Cheers,
 René



-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159