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why 2 diodes connecting in series; one forward biased and another reverse biased.

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sys_eng

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if two in series; one forward and another reversed. then no current would flow either way through in any situation unless you cause a avanlanch break down and ruin one of the diode?
 

I tested a 50V diode, measuring reverse current through it. Not even 1uA got through. If I had gone over 50V, I think it would destroy the PN junction. Or is it like a zener? I've never heard the reverse rating described as a zener voltage.

It would be an interesting experiment to send 1uA through a diode momentarily, to find out if it ruins it, or merely changes its operating characteristics.
 

I tested a 50V diode, measuring reverse current through it. Not even 1uA got through. If I had gone over 50V, I think it would destroy the PN junction. Or is it like a zener? I've never heard the reverse rating described as a zener voltage..

A typical diode, 1N4001 has several uA of reverse current at the rated reverse voltage. This also increases with temperature exponentially. If you did apply only a couple of volts, the current will be about 0.1uA (guessed from the graph; I did not measure)

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if two in series; one forward and another reversed. then no current would flow either way through in any situation unless you cause a avanlanch break down and ruin one of the diode?

Such double diodes are often used as part of a bridge circuit (or a full wave rectifier).
 

If you are talking about devices like the BAT54A or the BAT54C, these are building blocks for full rectifier bridges.
 

if two in series; one forward and another reversed. then no current would flow either way through in any situation unless you cause a avanlanch break down and ruin one of the diode?
You are not mentioning a center tap connecting anywhere. So the answer is simple, the circuit makes only sense for zener diodes.
 

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