Power supply is called too as an adaptor has a great function in electronics circuit. A full wave power supply can be implemented by a step-down transformer,  4 pieces of diode and one piece of capacitor (as seen at Figure 1).

Figure 1. A simple power supply circuit.

Output voltage of circuit at Figure 1 is good enough for supplying several of general electronics circuit, but for specific circuit that need a good enough voltage regulation is not meet, so we need a voltage regulation such as seen at Figure 2. Output voltage at Figure 2 is depended on IC 78xx, if we need 5 volt output then we can to use LM7805, with input voltage is greater than 5 volt (as the voltage tolerance that specify in its data sheet, visit at download page).

Figure 2. Circuit of regulated power supply using IC LM78xx.

To increase the output current that flows out the power supply (using IC 78xx) then IC LM78xx could be connected to power transistor in parallel way such as  seen at Figure 4. Figure 3 is a regulated power supply which the output voltage is changeable.

Figure 3. Output changeable regulated power supply.

Figure 4. Greater output current regulated power supply.

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