Using a FET to switch a higher current.

[Ray]

Hi!

I am trying to use a simple FET to switch on a higher current that runs
a small electric motor, but I'm not sure if I have it set up right.
What do I hook up to the drain/source/gate? I'm not really sure what
these are. There is also a metal block on top of the FET that it looks
like I could connect wires to. Is there maybe a website tutorial for a
complete novice when it comes to using FETs? Any help is greatly
appreciated. Thanks!

 

[PeteS]

Hi!

I am trying to use a simple FET to switch on a higher current that runs
a small electric motor, but I'm not sure if I have it set up right.
What do I hook up to the drain/source/gate? I'm not really sure what
these are. There is also a metal block on top of the FET that it looks
like I could connect wires to. Is there maybe a website tutorial for a
complete novice when it comes to using FETs? Any help is greatly
appreciated. Thanks!

There are, as you noted, 3 terminals. How you connect them depends on
the circuit. The gate is usually the control terminal. Drain and source
connections depend on other things in this case, so it's not possible
to say.

Beyond that, I don't think I can help without knowing the part and more
details of the application.

Switching high or low side?
Run current?
Run voltage?
(You'll have to protect against reverse emf too)

For a search, google is your friend:
http://www.google.com/search?source...-8&rls=GGGL,GGGL:2006-19,GGGL:en&q=fet+basics

(FET basics)

In this particular case, you are probably using a MOSFET, so :
www.irf.com/technical-info/appnotes/mosfet.pdf (A little more advanced
than very basic)

Search under 'MOSFET basics' and you'll bring up thousands of hits.

Do that, then come back and ask some more. We tend to be more
forthcoming for people who have done at least some legwork trying to
figure things out.

Cheers

PeteS

 

[Fred Bloggs]

I am trying to use a simple FET ....

Why do you call it "simple" when you don't have the least idea what it
is, what it does, or how to go about using it? You're an arrogant
pea-brain from hell.

 

[Damir]

Hi!

I am trying to use a simple FET to switch on a higher current that runs
a small electric motor, but I'm not sure if I have it set up right.
What do I hook up to the drain/source/gate? I'm not really sure what
these are. There is also a metal block on top of the FET that it looks
like I could connect wires to. Is there maybe a website tutorial for a
complete novice when it comes to using FETs? Any help is greatly
appreciated. Thanks!

sci.electronics.basics

 

[Mr.J Dizzle]

Hi!

I am trying to use a simple FET to switch on a higher current that runs
a small electric motor, but I'm not sure if I have it set up right.
What do I hook up to the drain/source/gate? I'm not really sure what
these are. There is also a metal block on top of the FET that it looks
like I could connect wires to. Is there maybe a website tutorial for a
complete novice when it comes to using FETs? Any help is greatly
appreciated. Thanks!

To make it as simple as possible a MOSFET is like a transistor except
that it is controlled by a voltage, and it isnt variable like a
transistor is, it is only ON or OFF. This site gives some more info:
http://www.mtmi.vu.lt/pfk/funkc_dariniai/transistor/mosfet.htm

 

[Steveo]

To make it as simple as possible a MOSFET is like a transistor except

Huh? Actually, the "T" in MOSFET stands for "Transistor". A MOSFET is
a transistor. I'm not sure where you got the idea that it's not.
Technically speaking, MOSFET's have more regions than the two you
mentioned, which are saturation and cut off. But low power electronics
use the region between these two, and there's still reverse saturation
and others to think about.

If you are designing digital electronics, then maybe these are the only
two states you use, but there are many more states to choose from.

 

[Ken Smith]

Huh? Actually, the "T" in MOSFET stands for "Transistor". A MOSFET is
a transistor. I'm not sure where you got the idea that it's not.
Technically speaking, MOSFET's have more regions than the two you
mentioned, which are saturation and cut off. But low power electronics
use the region between these two, and there's still reverse saturation
and others to think about.

It isn't just "low power" electronics that run MOSFETs in linear mode. I
have designed more than one MOSFET based linear regulator.

MOSFETs have the advantage of not having a 2nd breakdown so you get more
time to shut them down in the overload case.