Re: Quick question on FETs
- From: Wimpie <wimabctel@xxxxxxxxx>
- Date: Sat, 11 Jul 2009 06:41:34 -0700 (PDT)
On 10 jul, 22:24, Jon Kirwan <j...@xxxxxxxxxxxxxxxxxxx> wrote:
On Fri, 10 Jul 2009 11:20:43 -0700 (PDT), "keith...@xxxxxxxxx"
<keith...@xxxxxxxxx> wrote:
On Jul 10, 12:26 pm, Jon Kirwan <j...@xxxxxxxxxxxxxxxxxxx> wrote:
On Fri, 10 Jul 2009 06:26:05 -0700 (PDT), "keith...@xxxxxxxxx"
<keith...@xxxxxxxxx> wrote:
On Jul 10, 7:58 am, Andrew <andrewkgent...@xxxxxxxxx> wrote:
Hello,
I do a fair amount of microprocessor design where I use the processor
output pins to drive BJTs. I usually use a 2N222 for switching small
devices, and a TIP122 for larger devices. I would like to wean myself
off of the BJTs and start using FETs to accomplish the same task. But
I have never used FETs (other than in school). Can anyone give a part
number(s) for a FET which could be used to replace a TIP122?
thanks,
Andy
We use IRLML2502s for general purpose stuff, from driving LEDs to
relays.
Hmm. I hadn't seen it before. Vgs(th) max of 1.2V and can cost under
20 cents in some modest qty. Still, I got pn2222 for well under one
cent. Of course, other components are usually needed. So I'm keeping
this one in mind and buying some soon to try out.
With an Rds(on) of ~50mohm, it can handle a fairly hefty load, too.
With a base drive that many micros can handle, a pn2222 can do several
hundred mA with Vce of a few tenths volt. I usually experience a beta
of about 50-100 at useful saturation levels (1/4 volt Vce.) More like
an ohm, though, I suppose. Cheap.
But yes, I like the idea where handling more current is required and
this part looks very nice because it works with a variety of low
voltage micros and is not over-priced.
Thanks,
Jon
When you have to switch low voltage loads in the Ampere range, you can
use the "low VCEsat" transistors (NXP/philips, Zetex/diodes). These
devices have high HFE (>200), very low VCEsat and can be driven from
1.8V logic.
Best regards,
Wim
PA3DJS
www.tetech.nl
please remove the obvious three characters in case of PM.
.
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