[sdiy] generating an s-shaped curve

[Scott Gravenhorst]

Harry Bissell <harrybissell at wowway.com> wrote:
>OK let me explain. I want to process a CV, so that there is 
>increasing (non-linear) gain for signals above a break point 
>(maybe +1V) and that has (well) increasing gain going negative 
>below that. 
>
>The idea, the 1V signals would be unaffected by the circuit, 
>higher voltages would go progressively higher, and lower voltages 
>would go progressively lower. 
>
>I can think of a diode breakpoint generator, but I'm looking for more ideas :^)
>

Not sure if this is useful - but a CMOS 4069UB or 4007 gate operated as a linear amplifier
has a nonlinear gain function which is dependant on the input voltage to the gate.  The gain
is highest at (Vdd-Vss)/2 and lowest near either rail symmetrically.  For example, if a
triangle waveform is input to the linear amplifier, the slopes in the output will be spline
or sigmoid shaped.

-- ScottG
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-- Scott Gravenhorst
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