Re: Need higher speed 2N7002

John Larkin wrote:

On Tue, 16 Jan 2007 14:53:52 -0800, Joerg
<notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote:


Winfield Hill wrote:


John Larkin wrote:


Harry Dellamano wrote:



The 2N7002 has served me well for many years but at 20MHz general purpose
switching the 30nS rise times are just too slow by an order of magnitude.

I'm getting < 3 ns output edges from 2N7002's at 50 volts drain swing.
You do have to drive a low impedance load, and you do have to drive
the gate hard. In the over-20 volt range, within its current
capability, I've found nothing faster, at least in silicon. My working
model of a 2N7002 is an infinitely fast mosfet with source and drain
capacitances and some wirebond inductance.


Agreed.

There may be a slightly better part, but circuit changes to improve
risetime from 30ns to the 3 to 5ns territory are not very difficult.


It's the same with high voltage FETs where I sometimes have a hard time convincing people to at least try it. Which makes me wonder why FET datasheets are so very conservative WRT switching times.


Please KEEP QUIET ABOUT THAT. Sheesh, we want every else to keep
believing those datasheets.

We did some stuff with Moto 400-volt TMOS-7 fets that was so fast we
had to add gate resistors to slow them down.


I even had to do that to the old BSS123 once because we would have blown through an EMI limit otherwise.

My favorites are those TV tuner transistors. What they can do for a mere five cents is amazing.

--
Regards, Joerg

http://www.analogconsultants.com
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