[sdiy] Newbie question: Diode ladders

[Colin f]

> Hi. I don't understand how a diode ladder works as a voltage 
> controlled resistor (i.e. in a filter). Somebody enlighten me 
> (with a LED?) please! o]:-)
>  
> Are you using the linear area of a non-ideal diode or what?

It takes advantage of the dynamic resistance of the diode.
There is a nice explanation on this page...
http://www.innovatia.com/Design_Center/Transistors.htm
...much easier than trying to draw curves in ASCII.

Cheers,
Colin f