Dual Polarity Regulated Power Supply

Figure 1 

The circuit design of this dual polarity power supply is regulated with the use of a positive (78xx) and negative (79xx) voltage regulators.

Dual polarity power supply are created mostly to power up operational amplifier circuits and other circuits that require dual supply voltage. The voltage is adjustable, requires a few parts, and easy to build. The circuit utilizes 7815 regulator for the positive supply while 7915 voltage regulator for the negative supply.

The monolithic IC 7815 positive voltage regulator is designed for use in several ways of applications including on board regulation. It makes use of internal current limiting, safe area compensation and thermal shutdown. It can produce output currents in excess of 1 Amp with enough heat sinking. It can be used with external components to obtain flexible voltages and currents, although it is designed primarily as a fixed voltage regulator. The negative voltage regulator 7915 employs the same features as with 7815 which makes it also notably rough for any operating conditions.

The rating of the transformer’s primary depends on the region of the supplied voltage. To allow losses on both regulators, the secondary coil should be 18 volts at 1 amp rating. Since the circuit might operate under 120, 220 or 240 volts, it’s a prerequisite for the circuit to be enclosed in a case where fans or heat sinks were usually required.