Ideas for a new circuit

[Magnus Danielson]

>>>>> "jb" == jorgen bergfors <jorgen.bergfors at idg.se> writes:

 jb> Hi synthesists.
 jb> In an idea for a new synth module, I need a circuit that peaks at a certain 
 jb> input voltage and then reduces it's output for higher and lower voltages.
 jb> The output shold be a voltage, say 5 volts, at 2 volts and then gradually 
 jb> decrease in amplitude to 0 volts when the input reaches 1 and 3 volts. Above 
 jb> and below that, it should have no output. 
 jb> It should be fast enough to follow audio input signals.
 jb> Any circuit ideas?

YES!!!

What you need is a precision rectifier cursuit and some additional
summer cursuits.

The clue to the solutions comes from a quick plot of the function you
are trying to describe:

  |
  |   /\
  |  /  \
  | /    \
--+---------
  /        \

Now, to get this function with an precision rectifier which has (in a
unmoded case) the following function:

 \   |   /
  \  |  /
   \ | /
    \|/
-----+-----

So, at the input one will adjust an pot to an summing amp moving the
flip-point left-rigth. One has the precission rectifier, an switch to
select top or bottom flip (you described a top flip) which just feeds
the precision rectifier output to either positive or negative input of
another summing amp which also takes a CV from a pot which moved the
flip point down-up. You can have both pots being added with external
CV with no trouble.

It whould work well throught out both your modulation, subbase and
audio range.

Voila!

Cheers,
Magnus