Using multiple regulators in a circuit?

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Paleoneon

New Member

• Oct 5, 2008

• #1

I'm making a circuit that will need both 12V and 5v rails. Can I put a couple of 7805 regulators in parallel for the 5V rail if I need more than amp or so of regulated 5V current?. The 12V source can supply plenty of current to the7805s.

 

Hero999

Banned

• Oct 5, 2008

• #2

It can be done but isn't recommended as it could be unstable and oscillate.

It's much better to use a series pass transistor, see the datasheet for details.

 

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Paleoneon

New Member

• Oct 5, 2008

• #3

Thanks Hero. I should've looked more carefully at the datasheet in the first place.

 

blueroomelectronics

Well-Known Member

• Oct 5, 2008

• #4

You could use a 78S05 and a decent heatsink.

 

S

Speakerguy

Active Member

• Oct 5, 2008

• #5

You can use LT1083/1084/1085 regulators, but you can't use ceramic output caps with them.

 

Last edited: Oct 5, 2008

Mikebits

Well-Known Member

• Oct 6, 2008

• #6

Check this article from EDN.
**broken link removed**

 

D

Dean Huster

Well-Known Member

• Oct 6, 2008

• #7

Or, you can use multiple 7805s with a small (e.g., 1 ohm) resistor in series between EACH output lead and the 5v bus. That small resistor will allow a small voltage drop between disagreeing regulators and allow them to better share the current at the cost of adding a little "softness" to the supply.

Dean