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lowest leakage, lowest Vf diode?

L

legg

Jan 1, 1970
0
What's it for indeed! Some special circuit configuration may be
able to handle the problem. For example, two 1n5822 diodes in
series will drop about 450mV at 100mA, and the connection node
between the two diodes can be bypassed with a resistor to ground
for the purpose of diverting most of the leakage current of the first
diode with 13 volts across it. If the resistor is a low enough value
the voltage drop across it from the first diode's leakage will be low
enough to avoid creating much leakage across the second diode.

Yes. Does he mean leakage, or Diode leakage. Any control circuit for
an active implimentation will obviously exceed the leakage mentioned.

Too bad these guys don't follow up their original posting.

RL
 
L

legg

Jan 1, 1970
0
Do you not mean "not in the datasheet"?
The nanoamp region is very achieveable.
Since the OP wanted a low Vf diode, the problem with FETS is that the
gate control is sensitive to temperature, so a fixed bias scheme for
enhancement *or* depletion mode FET is a bit iffy - especially in this
case where the gate control voltage is going to change only a few
hundred millivolts.
Now that temperature sensitivity can be compensated some with a
scheme similar to my first Codatron (TM) design; the patent for that has
been released into the public domain - so feel free to use as you see fit.
Be advised that there can be some mis-matching between FETS, so that
for this "low Vf" application, that can have a large effect on the total
operation if multiple composite devices are needed (read: volume
production greater than 1000 per day).
That can be mitigated to a degree by making it as IC, wafer testing
offset before breakout and use.
Shoot, one could even trim one of the FETs my having graded sizes for
cutting out small areas; and the bias offset can also be trimmed (refer
to the ALD110800 series).

Any control circuit for an active implimentation will obviously exceed
the leakage mentioned.

Too bad the guy doesn't follow up the original posting, so we could
find out what is actually needed. Asking non-ideal parts to do ideal
work is a trick that we all handle daily.

RL
 
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