A low reverse current junction

[hsuang]

I need a diode with a reverse current smaller than the classic small-signal diode (as couod be a BAS16 and so on), but still common as it.
I think the best solution is using a (symmetrical?) FET with the gate as anode and source + drain as cathode...
But if I was choosing a BJT, what's the best connection? Using (NPN) base as anode and collector as cathode, should I leave the emitter floating or connected to base?
Could someone explain this subject?

Many thanks

Francesco

 

[btbass]

The diode junction is between base and emitter.
So you would connect base and collector as anode and emitter as cathode.
One problem is the low reverse voltage breakdown between emitter and base.
Typically ~3V.

I don't think your FET circuit would work using just the gate as anode.
The gate is insulated so no current can flow.

 

[hsuang]

Hi BTBASS,
the base-emitter junction is not so good in terms of reverse current, the base-collector one is surely better...

However the breakdown of the base-emitter is about 6..8 V, not about 3 V.

Moreover: the FET (I mean Junction FET, not MOSFET ) have a pretty good diode, with a reverse current hundreds lower than a "normal" signal diode

 

[karesz]

Hi hsuang,
Maybe FD300 is some thing for you?
K.

 

[hsuang]

The FD300 seems not to exist anymore...
This topic is not about a particular device, but on the best way to use a standard device, such as a common NPN small signal BJT, to achieve a low reverse current diode (typically for instrumentation pourpose).

Francesco

 

[karesz]

Aha,
I think, this was (for me)not enough clear wroten...
But, what about similar types, you can find lot of through searches, i.e..: BAS416 Low-leakage diode, than CMAD6001 05/08, Ultra Low Leakage Diode SOD-923(500pA! is eough low for you too_or?)...
Good luck!
K.