From: Robert Baer
X-Mailer: Mozilla 4.75 [en] (Win98; U)
Subject: Re: Lowest voltage drop diode
Date: Wed, 25 Sep 2002 07:19:59 GMT
NNTP-Posting-Date: Wed, 25 Sep 2002 00:19:59 PDT
Organization: EarthLink Inc. -- http://www.EarthLink.net
> 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.
> Currently, I am using a BAT85 Schottky diode from Philips. This has a
> forward voltage drop of 0.3-0.4 Volts maximum. I have looked at some
> Germanium diodes that have a drop of 0.3 Volts.
> Is there a way to do this with a MOSFET or Transistor ?
> Is a one-way conducting device of 0.2 Volt drop or less achievable by
> any means ?
> Oguz Murtezaoglu
> BiPOM Electronics
1) The tunnel rectifier has a *very* low drop; near zero.
The "reverse" voltage "breakdown" is near 300 millivolts.....
What this is, exactly, is a tunnel diode with "no" peak current, and
Referring to standard TD configuration, the reverse characteristics is
close to a wire, and the forward characteristic is very close to that of
a germanium transistor.
So, reversing it and naming it a tunnel rectifier, one gets very low
forward drop, and pays the penalty of that 300 millivolt conduction.
2) All that aside, one can get partly inbetween, by using a germanium
transistor with the base tied to the collector.
With decent beta transistors, the forward drop of this configuration
(called a DCT or Diode Connected Transistor) one may achieve near 150mV
drop at 5mA.