Re: MOSFET question: Drive voltage vs. Vgs(th)

accolade@xxxxxxxxx wrote: 
Can anyone tell me the difference between the drive voltage and the
gate-to-source threshold voltage (Vgs,th) of a MOSFET, if any?


I was under the impression that these refer to the same voltage - the
voltage that is needed to turn the MOSFET 'on'.
However, if you look at the following data*** for a Fairchild
MOSFET...


http://www.fairchildsemi.com/ds/FD%2FFDG311N.pdf


you'll see that the title says "2.5V Specified", which I understand
refers to the drive voltage. However, under the "On Characteristics,"
you'll see Vgs(th) min. = 0.4V and Vgs(th) max. = 1.5V. Why isn't
Vgs(th) max. = 2.5V, as the title suggests? Is there a difference
between Vgs(th) and the "specified voltage"? 


Thanks!

the threshold is simply the critical point of operation and you
normally don't want to rely on that..
  normally it's good practice to go above that threshold to insure
reliable switching.
  it's best to drive them with an acceptable level well above the
threshold.
 in this case of your choice, i would say 2 volts is good..
i noticed that it will handle up to 8.


--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

.