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How do I use a negative voltage regulator? Answered

I have some 7905C voltage regulators, and I'm wondering if I can use them the same way I would use a 7805 voltage regulator except on the opposite side of the circuit.

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gmoon (author)2011-04-29

Use two 7905 regulators for a bipolar supply, instead of a 7805 & 7905 pair?

Years ago I tried two 7812 regulators in much the same way. It sort of works, but the minus voltage deviated by ~0.5V and was noisy.

I believe that the 78xx and 79xx both use the same (middle) ground as a reference for the regulation. Two 78xx or 79xx's in a pair will share one ground, but two different regulation references.

In other words--there's gotta be a good reason why they make two separate regulators...

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AndyGadget (author)2011-04-29

Yes, you can,but unless you actually need a negative voltage (i.e. you're using positive voltages as well) you'll need to connect the positive rail of your circuit to the 0V of the regulator and the 0V of your circuit to the -5V of the regulator.  Confusing, but it will work.  Don't forget to connect the capacitors the correct way around as well (+ve to 0V, -ve to -5V).

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