On Thu, 9 Feb 2006, David VanHorn wrote:

>> No. Typically SPICE diode models turn on instantly when forward biased.
>
> Score another one for simulation!  :)
>
> Isn't this an interesting little problem?  Amazing how something that seems
> this simple can be so tough to put a finger on.

It is not so simple because the diode is already sort of 'on' when made. 
It's just that without an exernal voltage source it is *reverse* biased. 
So to turn on it has to recover from that (0.6V) reverse bias situation. 
So a ton rating would be trr for I=0.

But I am fairly sure that the inductance of the leads and such prevents
any picosecond speeds. Usually a maximum speed is given for devices. For 
1N4148 this is 100MHz afaik. This implies both ton and toff not longer 
than 5nsec.

Peter


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