[sdiy] Bending a Sum

[Tom Bugs]

Thanks All.

Well,, , these ideas that Paul suggested (and other similars I'd seen 
searching LOG amp) - I did get something seeming to work a bit going in 
the simulator (no chance to try in real life)

I don't think that temp stability actually would matter in THIS application.

But, yeah, think I'm probably going to part rip-up the design and try 
again using linear but in a somewhat different circuit approach -- 
fitting things on the outputs, I had to have three VCA sections all from 
the same control and then an independent 4th VCA -- think I may be able 
to change things around and just have 2 linear vcas around the input areas.

Was worth me thinking about this even if I/we didn't come up with a 
simple solution.

Ta!Tom


On 19/11/2013 02:56, Paul Perry wrote:
> Cheap?
> Diode function generator (AKA breakpoint function generator) might be 
> what you want.
>
> Basically, it's an amplifier that changes gain when various diodes 
> switch on or off,
> which is dependant on the input voltage.
>
> an elaborate one here: 
> https://www.circuitlab.com/circuit/g2u947/simple-piecewise-linear-approximation-using-diode-function/
>
> But it might be possible to just use a transistor in a feedback loop, 
> as here:
> http://www.circuitstoday.com/log-amplifier
>
> paul perry Melbourne Australia
>
>
>
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