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Sunday, November 14, 2010

Adjustable power supply 0.1V – 50V By CA3130 and 2N3055

This power supply circuit is highly stabilized that its output voltage will drop only 0.005% even though the load changes from 0 to 100%. Another excellent capability is that the output voltage will change only by 0.01% if the input voltage fluctuates. The capability if the circuit to be adjusted from 0.1V up to 50V is due to the application of opamp IC CA3130 in the circuit. Transistor T4 raises the output voltage to higher level, and at the same time it separates the lower level opamp from the high level of the output voltage. The reference voltage is supplied by IC1. It is a temperature compensated transistor array with 5 transistors. Four of these transistors are used as reference diodes and the fifth one sets the output impedance of the reference source.

The reference voltage is set through P1. The opamp CA3130 compares the reference voltage at its minus input to the output voltage at its input. The output voltage passes first through a voltage divider before it is fed into the plus input of the opamp. Transistors T1 and T2 work as darlington pair and amplifies the current. Transistor T3 functions as current limiter. The current limit is ajustable through P1, and the lowest current limit is 0.6 ampere. Once potentiometer P1 is set at maximum, current limiting is disabled.