Talk:Reverse leakage current
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I believe the reverse leakage current (in BJT's) or reverse-bias saturation current (in diodes) is independent of the voltage across the device (although there are two names, they are caused by the same phenomenon) and is not present in other transistor types (such as the MOSFET). It is caused by minority carriers (positive charge in the N-type region, negative charge in the P-type region) that are able to drift across the P-N junction. The magnitude of the current is dependent on two of the device's physical properties: (1) doping concentration; (2) area of the P-N junction. It is a non-ideal effect.
Recall the equation for the current in a diode is something of the order: ID = IS(eblah - 1)
Where ID is the resulting current in the diode, and IS is the reverse-bias saturation current.
The reverse leakage current is very small (in the range of ferroamps, give or take), but is always subtracted from the forward current (because of the -1 term in parenthesis). When the diode is forward biased at a large enough voltage, the exponential term dominates the equation (sorry, I left the details out of this term, but the voltage across the diode is in the 'blah' term, increasing the voltage makes the exp. term larger) and the forward current is much larger than the leakage current.
For example, at a sufficient forward bias, the forward current may be in the range of mA and the reverse current in the range of fA. The reverse current is so small in comparison, that for practical purposes, it can be ignored. But it is always there!
For those who want to lurk further into the theory behind this, there are two types of current; the forward diode current is called a 'diffusion' current, the reverse leakage current is called a 'drift' current.
I hope this helped more than it hurt... peace.
-Ryan
