Analog Exp (Antilog) vs Log

[juz_ad]

If you graph the functions exp(x) (left) and log (x) (right) you get the curves below as expected.



If you use an Antilog (exp) circuit you get the curve below as expected:



So - would a Log circuit give this as it's output (and if not - what circuit would)?



Thanks.

[Edit: so after an hour of not getting very far, as soon as I posted this I started getting results. Looks like, with some inversion and biasing, it should work as hoped. I'd still appreciate any input/advice on reproducing the inverse of the exp curve though. Thanks.]

 

[FvM]

I don't see a log function plot in the third curve, only y = -exp(-x). It would be of course generated by an antilog circuit, as you apparently did. Nice try to fool people at edaboard.

 

[erikl]

... would a Log circuit give this as it's output (and if not - what circuit would)?



Thanks.

[Edit: so after an hour of not getting very far, as soon as I posted this I started getting results. Looks like, with some inversion and biasing, it should work as hoped. I'd still appreciate any input/advice on reproducing the inverse of the exp curve though. Thanks.]

I think this is V = V0*(1-exp(-nx))

i.e. an RC discharge curve, display mirrored at point (x=0.5 ; y=0).