Dual-rail Variable DC Power Supply

This design was conceived as an add-on for the Variable DC Power Supply, a very successful circuit posted to this website. This simple unit provides a dual-rail variable output ranging from ±2.5V to ±15Vdc with precise tracking of the positive and negative output voltages, still retaining the current limiting and short-proof capabilities of the "master" circuit. As the purpose of such a dual-rail design is to supply experimental or under-repair circuits, the maximum current output delivered was deliberately kept to about 500 - 600mA per rail, thus avoiding the use of expensive power transistors and complex circuitry.

• R1 = 4.7K-1/2W
• R1 = 4.7K-1/2W
• C1 = 100nF-63V
• C2 = 220µF-25V
• C3 = 220µF-25V
• C4 = 100nF-63V
• C5 = 100nF-63V
• Q1 = BD437
• Q2 = BD438
• IC1 = LM358