Dual Polarity Power Supply

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This dual polarity power supply is easy to build, requires few parts, and is adjustable from 0-15 volts. It is great for powering op amp circuits, as well as other circuits that require a dual supply voltage.

Schematic

Parts

Part	Total Qty.	Description	Substitutions
C1, C2	2	2200uF 35V Electrolytic Capacitor
C3, C4, C5, C7	4	1uF 35V Electrolytic Capacitor
C6, C8	2	100uF 35V Electrolytic Capacitor
R1, R4	2	5K Pot
R2, R3	2	240 Ohm 1/4 W Resistor
BR1	1	2A 30V Bridge Rectifier
U1	1	LM317 Adjustable Positive Regulator
U2	1	LM337 Adjustable Negative Regulator
T1	1	30V Center Tapped 2 Amp Transformer
S1	1	SPST 2 Amp Switch
MISC	1	Heatsinks For U1 And U2, Line Cord, Case, Knobs For Pots, Wire

Notes

Since this project operates from 120 (or 220, or 240, etc.) volts AC, it MUST be built inside a case.

U1 and U2 get quite hot and will require heatsinks. A fan is usually not needed.

You can, of course, add a volt and amp meter.

U1 and U2 can only go down to a minimum of +-1.2V. If you need to go lower, you can add two 1N4003 diodes in series with the output of the regulator. The diodes drop about 0.6V each, which will allow the supply to go to 0. Note that this will also decrease your maximum output voltage by 1.2V. (Thanks to Steve Horvath for the suggestion).

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Comments

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anonymous Dual Polarity Power Supply Monday, May 20, 2013 7:30:52 AM

I simulated the above circuit in Multisim & found the load currents to be very low(about 0.5mA). Can u suggest a way to increase the load current to about 2A.

anonymous Dual Polarity Power Supply Friday, January 13, 2012 10:39:50 AM

Hi,i really need help on how to design a dual channel DC power supply that fulfills the following specifications : 1) Operation - User selection between independent adjustment for positive and negative output voltage, and series tracking mode (slave channel tracks the master channel) 2) Output voltage amplitude : 0-20Vďż˝ 5% 3) Current limit : 0 - 1.5Aďż˝ 10% 4) Powered Directly from main supply 5) Indications of power on, constant voltage and constant current mode I really hope you guys will be able to help me and provide me with a schematic to achieve the above specifications..thanks in advance =)

anonymous Dual Polarity Power Supply Wednesday, December 07, 2011 2:10:55 PM

Hi perhaps some one could design a pcb for the circuit and layout, it would make the authors design far more superior

anonymous Dual Polarity Power Supply Friday, November 05, 2010 7:37:50 PM

To the guy below. R1 and R4 are potentiometers. It's okay to leave one side unconnected.
(Editor's notes: Sure, if you want noise...)

anonymous Dual Polarity Power Supply Monday, October 18, 2010 10:04:13 AM

The R1&R4 where is it going to connect….. is it short circuit or what please answer

M.Khalid Ansari Dual Polarity Power Supply Wednesday, October 13, 2010 10:23:26 AM

I made this dual power supply two times but it doesn't work. Only transformer is heating up. After that I made single power supply by eliminating LM337 and other capacitors then it works properly. Please guide me, why dual power supply is not working?

Opcode Dual Polarity Power Supply Monday, August 16, 2010 2:33:53 AM

Better way to go below 1.2V (well, 1.25 to be exact) is to tie the R1 pot to -1.25V (instead of ground as shown) and R4 pot to positive 1.25V.

anonymous Dual Polarity Power Supply Friday, July 30, 2010 2:32:26 AM

can you please send me a circuit diagram of a dual power supply regulator to supply currents between 0 and 1.5A to a variable load resistor at a voltage of 2 to +12V

vp_archer Dual Polarity Power Supply Friday, June 25, 2010 12:02:14 AM

the junction between capacitors: are they connected to GROUND? from the diagram i see a "dot" there, but will that cause any problem? thank you.

anonymous Dual Polarity Power Supply Monday, December 21, 2009 11:11:48 AM

I want to know about the Input, Output and Ground of U1 and U2. I mean what are 1, 2, and 3. Can you reply it to my mail? Thank you.

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anonymous	Dual Polarity Power Supply	Monday, May 20, 2013 7:30:52 AM
I simulated the above circuit in Multisim & found the load currents to be very low(about 0.5mA). Can u suggest a way to increase the load current to about 2A.
anonymous	Dual Polarity Power Supply	Friday, January 13, 2012 10:39:50 AM
Hi,i really need help on how to design a dual channel DC power supply that fulfills the following specifications : 1) Operation - User selection between independent adjustment for positive and negative output voltage, and series tracking mode (slave channel tracks the master channel) 2) Output voltage amplitude : 0-20Vďż˝ 5% 3) Current limit : 0 - 1.5Aďż˝ 10% 4) Powered Directly from main supply 5) Indications of power on, constant voltage and constant current mode I really hope you guys will be able to help me and provide me with a schematic to achieve the above specifications..thanks in advance =)
anonymous	Dual Polarity Power Supply	Wednesday, December 07, 2011 2:10:55 PM
Hi perhaps some one could design a pcb for the circuit and layout, it would make the authors design far more superior
anonymous	Dual Polarity Power Supply	Friday, November 05, 2010 7:37:50 PM
To the guy below. R1 and R4 are potentiometers. It's okay to leave one side unconnected. (Editor's notes: Sure, if you want noise...)
anonymous	Dual Polarity Power Supply	Monday, October 18, 2010 10:04:13 AM
The R1&R4 where is it going to connect….. is it short circuit or what please answer
M.Khalid Ansari	Dual Polarity Power Supply	Wednesday, October 13, 2010 10:23:26 AM
I made this dual power supply two times but it doesn't work. Only transformer is heating up. After that I made single power supply by eliminating LM337 and other capacitors then it works properly. Please guide me, why dual power supply is not working?
Opcode	Dual Polarity Power Supply	Monday, August 16, 2010 2:33:53 AM
Better way to go below 1.2V (well, 1.25 to be exact) is to tie the R1 pot to -1.25V (instead of ground as shown) and R4 pot to positive 1.25V.
anonymous	Dual Polarity Power Supply	Friday, July 30, 2010 2:32:26 AM
can you please send me a circuit diagram of a dual power supply regulator to supply currents between 0 and 1.5A to a variable load resistor at a voltage of 2 to +12V
vp_archer	Dual Polarity Power Supply	Friday, June 25, 2010 12:02:14 AM
the junction between capacitors: are they connected to GROUND? from the diagram i see a "dot" there, but will that cause any problem? thank you.
anonymous	Dual Polarity Power Supply	Monday, December 21, 2009 11:11:48 AM
I want to know about the Input, Output and Ground of U1 and U2. I mean what are 1, 2, and 3. Can you reply it to my mail? Thank you.