[sdiy] Passive filters and impedances

[Rick Jansen]

I have not studied the thread extensively, so sorry if I drop in with random noise, but I happened to run into a situation where I needed diodes with a small voltage drop in the pass-direction, as to not lower a digital logic level too much. Schottky diodes have that! 0.25V forward voltage drop, for small currents, instead of regular 0.7V.

r.

> On 05 Nov 2015, at 13:48, Mattias Rickardsson <mr at analogue.org> wrote:
> 
> On 4 November 2015 at 22:16, Richie Burnett
> <rburnett at richieburnett.co.uk> wrote:
>>> Anyway - has this impedance scaling technique ever been used to full
>>> extent in any ladder filters, using different capacitor values for all
>>> stages?
>> 
>> You mean used in diode or transistor ladders?  I suspect not, as usually all
>> of the diodes or transistors operate at the same bias current, and would
>> therefore exhibit *the same* incremental resistance.  Not a decade apart.
> 
> Perhaps double diodes could be used in series or parallel to get
> double or half the resistance. Not a decade apart, but better than
> nothing? :-)
> 
> /mr
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