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.
Circuit diagram:
Parts:
R1 = 1R-2W
R2 = 10R-2W
C1 = 35v-470uF
C2 = 35v-470uF
Q1 = TIP2955
IC1 = 78xx Regulator
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