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[DPRG] increased output drive by CMOS and TTL devices

Subject: [DPRG] increased output drive by CMOS and TTL devices
From: R. Bickle rbickle at swbell.net
Date: Tue Jun 26 10:16:17 CDT 2001

Ben,

For this application, I would suggest simply using a small signal BJT such
as a Pn2222. You can drive this transistor directly from your logic output.
For a load of 24mA, you only need a base current of 0.024 / 100 = 0.00024A
or 240 microamps. You can use a 10K resistor at the base with plenty of
current at the collector. Be sure to add a reverse bias diode for those coil
transients!

BTW: Use the transistor to sink the coil, not to source it.

Good Luck
Rick Bickle


-----Original Message-----
>From: dprglist-admin at dprg.org [mailto:dprglist-admin at dprg.org]On Behalf
Of Ben Strednak
Sent: Tuesday, June 26, 2001 9:46 AM
To: dprglist at dprg.org
Subject: Re: [DPRG] increased output drive by CMOS and TTL devices


Gates are fun!

Jim, according to the datasheet, the 7400 can source 16mA.  Does that mean
16mA per gate?  I want to drive a relay that needs 24mA through the coil.
Thanks for all the help, everybody.

Ben

>>> Charlie W Youngblood <chaz128 at juno.com> 06/26/01 09:12AM >>>
Ben,
	Gates are fun. I once took a 7400 quad  2 input nand gate and
made
a flip flop (reeeeal technical term) out of half of it. I made a one shot
out of 1/4 of
it, and plugged it anto an amp thinking I was going to get some sort of
siren or
organ sound. Instead I was supprised to hear a radio station! Experiment,
play,
 & learn!
		Charlie Youngblood

On Mon, 25 Jun 2001 16:57:51 -0500 "Ben Strednak"
<Ben.Strednak at utsouthwestern.edu> writes:
>Hi folks.
>
>According to Forrest Mims, in his Engineer's Notebook, you can tie
>together the outputs of a CMOS IC to increase the amount of current
>the IC can source and sink.  For example, Mims uses a 4011 (quad nand
>gate), and connects all of the inputs of two gates to one another.  He
>then connects the two outputs to each other.  Can you do the same
>thing with TTL ICs and get the same effect?  More specifically, a
>74LS04?
>
>Ben
>
>
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