Vasile Surducan wrote:

> And the time when diode will switch, the voltage across it could be
> 
> u = L * di/dt
> 
> As long L is constant, t is direct dependent by switching time of
> diode but also by the transistor switching (that's why usually we
> choose a faster diode than 1N400x and not a standard lazy darlinghton
> but a switching transistor), [...]

How would a faster switching transistor reduce the voltage spike? Wouldn't
there be less of a spike with a slower transistor? In the extreme, if you
move the transistor slowly from on to off through its linear region, there
will be (almost) no spike at all. 

Gerhard

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