# Voltage Regulator

#### ELECTRONERD

Joined May 26, 2009
1,147
Hey Guys,

Could I use one of those power transistors as a voltage regulator? I would think to put a zener diode at the output to keep the voltage steady. I need a 12V 11A (continuous current) output. Would any transistors handle this current? Please show me how this is done!

#### Wendy

Joined Mar 24, 2008
21,906

#### ELECTRONERD

Joined May 26, 2009
1,147
Thanks Bill,

I would have multiple transistors, but how many do you think I would need for 11A? I could definitely get heatsinks and then also one of those compact fans found in hard drives.

#### Wendy

Joined Mar 24, 2008
21,906
Couple of points, what is the input voltage?

We've already established you want 11A 12VDC out.

This design has major flaws, there is a reason circuits with lots of components exist. You *might* be able to sqeek by if your load isn't too picky.

11A is going to get hot no matter what design you use.

#### ELECTRONERD

Joined May 26, 2009
1,147
Couple of points, what is the input voltage?

We've already established you want 11A 12VDC out.

This design has major flaws, there is a reason circuits with lots of components exist. You *might* be able to sqeek by if your load isn't too picky.

11A is going to get hot no matter what design you use.
Hey Bill,

I see... Well This depends on the transistors, their min and max voltages. I could have a 12V input and output... How would you go about this?

#### SgtWookie

Joined Jul 17, 2007
22,210
If you need a supply for that much current, you'll be better off getting a switching supply that's already built. Otherwise, you'll have quite a room heater.

Here are a couple of options from MPJA.com:
http://www.mpja.com/prodinfo.asp?number=16020+PS
12V @ 12.5A, $40.75+shipping. If you want to perhaps save some money and do some tinkering, you could start with this: http://www.mpja.com/prodinfo.asp?number=17383+PS 400W A-POWER ATX POWER SUPPLY 20/24 PIN It has a +12v output @ 15A,$21.95+shipping.
Then do a Google search for "ATX Bench Supply" for lots of ideas.

#### ELECTRONERD

Joined May 26, 2009
1,147
Thanks Wookie,

I do want to save money so that alternative looks good.

Thanks!

#### studiot

Joined Nov 9, 2007
4,998
11 amps, 12 volts.

If you don't mind my asking, what do you want to do with this?

I ask because some applications ( eg battery charging) don't require smoothing making any such supply that much easier, lighter, cheaper and more efficient.

#### ELECTRONERD

Joined May 26, 2009
1,147
I'm also an amateur radio operator and so I need this to power a 2-meter radio that I have (DR-140 by Alinco). With that power I'll be able to have an output 50W.

#### studiot

Joined Nov 9, 2007
4,998
There are others here with far better knowledge than I have of amateur transmitters.

Hopefully one of these will respond.

#### ELECTRONERD

Joined May 26, 2009
1,147
Awww...I just need `12V and 11A thats all. Your a WHOLE lot smarter than me .

Joined May 28, 2009
508
In radio sets, the amperage rating is the absolute maximum. I would suggest going with one of SGT Wookies ideas for power supplies. They would require a lot less effort to get your radio rig up and going. Plus, you don't have to engineer and build a power supply unless you want to. Obviously, you know that you need an FCC license to transmit on the amateur radio band, just throwing that out there for those who don't know.

#### Wendy

Joined Mar 24, 2008
21,906
Radio Transmitters do not respond well to switchers, their noise leaks through. You could use a gel cell to provide the current, assuming you aren't going to have this transmitter on continously, and trickle charge the battery when it's off. This would average out the current you need to something lower.

Bill

Joined May 28, 2009
508
If it has to be "RF Tight" can you put it in a metal enclosure and put some ferrite supressor beads on the input and output cables?

#### ELECTRONERD

Joined May 26, 2009
1,147
I will need capacitors probably on the output to supress some of the RF oscillations...

#### bertus

Joined Apr 5, 2008
20,102
Hello,

Did you see L1, L2 and C10 at the output of the schematic provided?
Also the metal housing is for making it RF tight.

Greetings,
Bertus

#### hobbyist

Joined Aug 10, 2008
887
Electronerd,
I thought you were extreeeeeemely new to electronics, thats why I was replying to your posts on transistor amps, (darlington amp thread) in a elementry way, but after reading this post your far above than what I thought. You probably understand this stuff more than me, when it comes to RF circuits I'm as far as just building little rf oscilators, that's about it.