What Zener Diode to use to reduce release delay?

RichardO

Joined May 4, 2013
2,270
I still like Richards, except to work with the Darlington it needs a reverse standard diode.
Are you sure? Rohm does not think so. ;)
They don't show the diode you mention... but they may not be showing the whole equivalent circuit in their spec sheet. You do have me wondering if the Zener will keep the transistor from saturating hard. I will have to think about it.
I did a simple simulation of the circuit with and without a low power Zener (and no extra diode) from the collector to the base of a Darlington transistor and did see an ever so slightly higher on-voltage with the Zener diode. In simulation the difference was less than 10 mv so I think that any power losses caused by the higher on-voltage are insignificant compared to the other methods that might be used.
 
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