Re: Simple problem: 0.20 V drop
- From: Jan Panteltje <pNaonStpealmtje@xxxxxxxxx>
- Date: Thu, 18 Jan 2007 14:54:09 GMT
On a sunny day (Thu, 18 Jan 2007 15:28:01 +0100) it happened Colin Howarth
<colin@xxxxxxxxxx> wrote in <eoo05d$1qc$01$1@xxxxxxxxxxxxxxxxx>:
Hi all,
This is a well-known problem (for those using old cameras...):
Mercury oxide cells have a pretty flat 1.35 V open circuit voltage.
They have however been banned in many countries. The best replacement
would seem to be silver oxide which has a voltage of 1.55 V.
the current drawn (by the exposure meter) is low.
So, I'd like to drop 0.20 V along the way somewhere.
a) Zener diodes: don't go down to 0.2 V
b) Schottky diodes: supposed to have a forward drop of 0.15 to 0.45 V
at 1 mA (according to wikipedia) but the drop is current dependent and
varies between samples.
c) Germanium diode?
If the current is constant, then a simple resistor + decoupling
capacitior will do.
Germanium drop is also a bit current dependent, maybe 150mV or so at
low currents (but less in the uA range).
.
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