[sdiy] Newbie question: Diode ladders

[Harry Bissell Jr]

My purpose was to illustrate that the resistance
really HAS to change. Its not something we can measure
with an ohmmeter. The other point is that as the
diode forwant drop stays reasonably constant over a
really wide range of current, the equivalent
resistance can vary by many orders of magnitude.

I was SO surprised when I first figured that out.

H^) harry

--- Ian Fritz <ijfritz at earthlink.net> wrote:

> At 09:07 PM 9/14/05, harrybissell wrote:
> >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.
> 
> 
> Hmmm ... to be a bit picky ... the dynamic
> resistance is actually the 
> tangent slope of the IV curve at the bias point. But
> for a rough 
> approximation using the chord, as you suggest, isn't
> too terrible.
> 
>    Ian 
> 
>