What are the equations for all those funny knobs?

Brian Towles gt7276a at prism.gatech.edu
Fri May 8 06:29:03 CEST 1998


> btw what ckt are you using?

I've been looking at some transconductance amp buildingblocks ( i.e.
LM13600 and CA3080 ) that I found in the
1984 IEEE Circuits and Systems maginize.  The author
outlines general first-order and second-order setups using
OTA's.  The most general form of the second order
configuration has 2 poles, 2 zeros -- all of which can be
indepedently voltage controlled.  However, the only two
parameters that I know of are resonance and cutoff.  I'm
guessing that both poles can affect the resonance.  Here's
what I think a popular LP freq. response would look like:

        /\     <--- "height", controlled by resonance
       /  \
-------    \
            \   <-- 12dB or 24dB
             \

           ^
           cutoff, controlled

Hope everyone enjoys my ACSII frequency response ;)

Maybe a good question is what other qualities of a basic
filter would be useful to change?  The general model I
have has 4 controllable parameters.  Any ideas?

Brian




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