Here is a simple power supply circuit that can be used for citizen-band and VHF walkie-talkies of power rating up to 10 watts. The circuit uses a step-down transformer, followed by bridge rectifier, filter, regulator, and current booster stages.
A pnp power transistor is added to the circuit to increase its current sourcing capabilities. Regulator 7812 can support
around 100 mA current. When the current
flowing through R1 nears 100mA value, the voltage (>0.65V) across the emitter-base junction makes transistor T1 to conduct and provide a path for additional current. The circuit can source around one ampere of current at 12+1.4 volts=13.4 volts. Both the regulator IC and the power transistor must be mounted on heat sinks.
A pnp power transistor is added to the circuit to increase its current sourcing capabilities. Regulator 7812 can support
around 100 mA current. When the current
flowing through R1 nears 100mA value, the voltage (>0.65V) across the emitter-base junction makes transistor T1 to conduct and provide a path for additional current. The circuit can source around one ampere of current at 12+1.4 volts=13.4 volts. Both the regulator IC and the power transistor must be mounted on heat sinks.
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