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From: email@example.com (N. Thornton)
Subject: Re: Lowest voltage drop diode
Date: 25 Sep 2002 16:44:40 -0700
NNTP-Posting-Date: 25 Sep 2002 23:44:40 GMT
firstname.lastname@example.org (oguz) wrote in message news:...
> I am looking for a very low voltage drop diode ( or equivalent circuit
> ) that has a forward voltage drop of 0.2 Volts or less. Maximum
> current to be conducted will be less than 5mA.
> Is a one-way conducting device of 0.2 Volt drop or less achievable by
> any means ?
1. Some silicon trs have V-ce-sat drops of around 0.15v - BFY51 I
think is one of them (not sure without checking it).
2. Running a si transsitor backwards gives much lower Vdrop still,
though with lower hfe and lower Vce max. (swap C and E)
3. germanium trs can beat 0.2v, and the base will work off the 0.2v
too, unlike silicons.
4. radio detector type diodes will conduct with less vdrop, some OA
type diodes. Look at specs on point contact and gold bonded types.
5. A relay (with diode in series with coil) is probably the lowest
Vdrop rectifier, but has many limitations.
6. Motor rectifiers give similarly low Vdrops. A synchronous motor is
used with a separate commutator producing suitably times connection,
resulting in effective rectification. The problem with that is what
happens as the motor is picking up speed :) Your electrolytics commit
7. Vibrating reed rectifiers also work, but are less than perfectly
8. I think metal rectifiers will pass some current at near zero Vdrop,
they don't have the sharp knee that modern ones have.
9. a reed relay can be used for some rect jobs.
10. Electrolytic rectifiers: I have no idea what their Vdrop is, but
some just might be able to work that low.
11. Numerous diode semiconductors from the days of crystal radio will
do less than 0.2v.
There are actually other (mostly wackadoo) rectification schemes
around as well. I wrote a paper on it one time.
If anyone can think of a use for little PCB mountable metal diodes...
let me know. I swear they must have _some_ use!
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