+/-100mA supply

Thread Starter


Joined May 14, 2006
I need a circuit that will give a variable +/-100mA output, floating load. Preferably +/-10V input. I have tried several 'ideas' but none seem to work. anyone built anything similar?
thanks guys


Joined Apr 19, 2007
I need to know the output voltage range...Give me more details (I.E. do you want it tracking or seperatly adjustable?) and I will work it out for you..Daniel.


Joined Apr 27, 2007
Is it a voltage source or a current source?

You can try using LM78XX, being XX the output voltage you want. For example, if you want 5V positive, try the LM7805. Those voltage regulators can support up to 1A with an adequate heatsink. Now since the input is 10V, you can use regulators giving up to 7V (LM7805, LM7806).
If you want negative potentials, you can use the LM79XX series.

Ron H

Joined Apr 14, 2005
You need to clarify your question. Do you want a single supply whose output can be varied +/-10V? Does it need to source and sink 100mA over the output voltage range? Or are you talking about dual (tracking?) supplies?


Joined Apr 19, 2007
Ah..That is the question I asked..Also 78xx and 79xx are not adjustable (well not on their own anyway)..If you wan't seperatly adjustable supplies, then the LM317 (for pos), and the LM337 (for neg) will be best.The voltage range on these is "int V.ref" (1.2 volts) to about "a volt and a bit" below the input voltage.To get them to zero, you have to use a ref voltage (- 1.2v for the 317), and + 1.2 v for the 337).That is why you can track them using a ref from each others output... Needs an op-amp as well)...I will design something, and post some schmatics over the next couple of days..Daniel.


Joined Apr 19, 2007
I have not foregten you..I have been a bit busy, but it will soon be here. (dual rail 0 to +/- 15 volt regulated, 1 Amp PSU).Daniel.