Drive an fet with a 555

Thread Starter

arthur92710

Joined Jun 25, 2007
307
I finally got some fet's
SUB85N02 but i cant get it to switch an led on and off with a 555. :mad:
I need some help
 

beenthere

Joined Apr 20, 2004
15,808
555's have no problem driving FET's. Can you post up a schematic so we can see what might be wrong? Sure the 555 is running?
 

Thread Starter

arthur92710

Joined Jun 25, 2007
307
its a n channel 20v mosfet in a To-263 package.
the pin out is G D S
g and s are long and d is short nut the metal back is also d
I have +9 on d (the case), 555 out on g the first one and a led then ground.

The led does not blink it just stays on.
 

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JoeJester

Joined Apr 26, 2005
4,075
Arthur,

The schematic, as drawn, works fine ... with the addition of a resistor in series with the LED.

There is a discrepancy between what you are saying and what your schematic shows. Clear up those discrepancies and add the values to your diagram.
 

Ron H

Joined Apr 14, 2005
7,012
With the way you have it drawn, your FET is a source follower, and will have several volts drop across it when it's on. If you reconfigure it as common source, it will be more efficient. See the circuit below.
EDIT: It came out really tiny. Not sure why.
 

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