3 to 24 vdc Power supply circuit with Op-amp

The regulated power supply can be adjusted 3 to 25 volts and is current limited to 2 amps as shown, but may be increased to 3 amps or more by selecting a smaller current sense resistor (0.3 Ohm). 2N3055 and 2N3053 transistors should be mounted on suitable heat sinks and the current sense resistor should be rated at 3 watts or more. Voltage regulation is controlled by half in IC 1558 or 1458 op-amp. 1458 may be replaced in the circuit below, but it is recommended that the supply voltage on pin 8 is limited to 30 VDC, which can be accomplished by adding 6.2 volt zener or 5.1 K resistor in series with the eighth pin Maximum DC voltage for 1458 and 1558 are 36 and 44, respectively. Transformer should be able to maintain the required current input voltage at least 4 volts higher than the desired output is, but higher than the maximum voltage op-amp for minimum load.

Power transformer is a center used 25.2 volt AC / 2 amps drive that will provide regulated outputs of 24 V at 0.7 amps, 15 volts at 2 amps, or 6 volts amps 3 amps to the third output is obtained using the transformer tap Wednesday with the switch to 18 volt position. All components should be available at Radio Shack, with the exception of 1558 op-amp.