How do transistors work?

[mindctrl]

Hi there,

I have no experience with transistors. How do you use them? I just bought three IRL520N N-ch MOSFET transistors, and I noticed they all have just three pins coming out from them? I'm confused. I have a +5v source coming through that I need to kick up to a 12V source with plenty of current, I am bringing the 12V through another part of my circuit... So basically there is a PIC that outputs 5v on one pin, and then it will hit the transistor, the transistor boosts it up to 12V with plenty of current, and then the LEDs will get their power from the transistor.

But with only three pins? How does this happen?

Thanks!

--mindctrl

 

[john1]

Hi mindctrl,

The IRL520N is an FET transistor (field effect)
from what i recall,
the main current path is controlled by the space-charge on the gate.

This is a very high impedance input.

(if ive got that wrong, someone will soon say so)

John

 

[john1]

Hi mindctrl,

well, ive had a bit of a look through the info on that,
and i'm not sure, but i think its a switching device, not an amplifier,
so it should be pretty suitable for driving reasonable loads on and off.

Which is what you appear to want.

John

 

[mindctrl]

Ahhhhh, gotcha. Thanks for the advice!

 

[samcheetah]

http://amasci.com/amateur/transis.html

 

[Roff]

You can drive LEDs as shown below. You can put LEDs is series, as shown, until (12V-N*Vled) is less than a couple of volts, where N is the number of LEDs in the series leg and Vled is the forward voltage drop of the LED. The series resistor value is R=(12V-N*Vled)/Iled. You can put multiple series strings in parallel, as shown. Without a heat sink, you should probably limit the total current through the MOSFET to less than about 3 amps.