|Semiconductor Physics was a while ago, so I don't remember if the
|Schottky junction trick is applicable to bipolar transistors.
|Usually, low forward drop is not an issue in bipolar transistors,
|since the controlled current (Collector current) is not flowing
|across a regular forward-biased PN junction.

That reminds me... one of the design features of a BJT is that,
unlike a MOSFET, it will only allow current to flow in one
direction while it is switched on.  So I was wondering...

If you have a supply of base current, what are the limitations
of using the BJT as a diode [between collector and emitter].
Obviously the transistor will only be on if the base voltage is
0.7 volts above (NPN) or below (PNP) the emitter voltage, but
in many applications this would not pose a problem if the drop
between collector and emitter is small.

For example, what would be the effects of replacing a blocking
diode on the positive leg of the power-supply input to a device
with a PNP transistor whose base was tied to the negative sup-
ply through a suitable resistor?  Would high-voltage transients
from the device be able to go backward through the transistor,
or would it not allow such things?



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