[sdiy] Newbie question: Diode ladders

[harrybissell]

If you use ohms law... and the fact that the diode forward voltage
is about .7V over a wide range of currents...

Take .7V / the current = the equivalent resistance of the diode.

Your signal levels have to be small enough that they don't move the
current much by comparison.

As far as illuminating you with an LED... you can use LEDs in a ladder
filter as well.  I tried it and it works, although they are hard to
match.

H^) harry

Colin f wrote:

>
> > 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