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Collector-Base diode of BJT as an Ultra low leakage protection diode

E

Ebrahim

Jan 1, 1970
0
Hello,
I want to know, is there anyone here that has used a BJT instead of an
ultra low leakage diode(<10pA) in a serious design. The reason that I do
not use JFET is that I need high breakdown(100V) voltage. So I also need
Bootstrapping for such a low leakage. I have done some measurements
with different JFETs and BJTs and I didn't find quit big differences.

Regards,
Ebrahim
 
E

Ebrahim

Jan 1, 1970
0
Yes; I think I mentioned that in another thread. I'm using BFT25's,
whose c-b junction is about half a pF and has reverse leakage of
roughly 30 fA at room temp and a few volts. That's hard to beat.

100 volts is trickier, but you should be able to find a small
transistor that will get you to a pA maybe.

A neon lamp gets interesting here.


Hello John :) ,
Thanks for replying to my post, How about bootstrapping? then voltage
won't be an issue(transistor c-b junction in series with a 1N4007).
collector current(Ic) of BF25 is just 6.5 mA which is too low, I need at
least 500mA.
It makes sense to look among high speed transistor which have lower
stray capacitance for such a purpose.
About neon lamp, that's also sound interesting, I will investigate about
that.

Regards,
Ebrahim
 
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