Ideas for a new circuit

[Tony Clark]

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

   So lessee if I follow you...

   First you'll be feeding an audio signal into an envelope follower to 
get a DC output according to signal level.
   Then I would feed that into a comparator, which compares the DC 
voltage to your 2 Volt reference (where you want the final output to be 
centered around) so that the output of this section is +/- depending on 
its relative position to the 2 Volt ref.
   Then I would feed this into a precision full-wave rectifier so that 
the output will be a positive going voltage (0V meaning that the DC 
output is at your 2V reference and 1V being +/-1V from your 2V 
reference).
   Then feed this into an inverter with a gain of 5 and an offset of +5V, 
and there you have it.  I'd also put a diode or something on the final 
output to prevent the signal from going negative (if that would cause a 
problem).

   Does that solve the problem?

   Tony

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I can't drive (my Moog) 55!         |     The E-Music DIY Archive
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Tony Clark -- clark at andrews.edu     | aupe.phys.andrews.edu/diy_archive
http://aupe.phys.andrews.edu/~clark |     Contributions welcomed!
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