Variable ramp generator

[Paul Maddox]

Don, et al,

>    a control voltage from, say, -1.0 volts to +1.0 volts,
>    two output currents, Iout1 and Iout2
>    1/Iout1 + 1/Iout2 should remain constant (at 1.0mA, we can scale later)
>    Iout1 should start near 1.0mA at Vc = -1.0V
>       hit 2.0mA at Vc = 0V.
>       hit some high value, say 15mA at Vc = +1.0V
>    Iout2 should go in the opposite direction
>
>There's an exponential equality that is very useful here:
>    1/(1 + exp(A)) + 1/(1 + exp(-A)) = 1
>

why not use two OTA's.. and a couple of log convertors? as found in most 
SVvcfs?

you could in theory, just use one log converter to drive a current mirror, 
take the output of the log convertor to one OTA and the output of the 
current mirror to drive the other?

Does this help any?

Paul



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