Small and very useful circuit, Can be built on a veroboard
Volt regulators such as the LM708, and LM317 series (and others)
sometimes need to provide a little bit more current then they actually
can handle. If that is the case, this little circuit can help out. A
power transistor such as the 2N3772 or similar can be used.
The power transistor is used to boost the extra needed current above the maximum allowable current provided via the regulator.
Current up to 1500mA(1.5amp) will flow through the regulator,
anything above that makes the regulator conduct and adding the extra
needed current to the output load. It is no problem stacking power
transistors for even more current. (see diagram). Both regulator and
power transistor must be mounted on an adequate heatsink.
R1 = 1R-2W
R2 = 10R-2W
C1 = 35v-470uF
C2 = 35v-470uF
Q1 = TIP2955
IC1 = 78xx Regulator