0.1V to 50V Variable Power Supply

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.

Adjustable power supply circuit schematic 50 volts power supply


Join the conversation!

Error! Please fill all fields.
  • yehuda

    how do i get the simulation of this circuit?

  • omry

    what should be the values of P1 and P2 to get an output voltage of 30V,20V and 10V ?


    What I do have against this circuit’s current limiting is that if the wiper of the limit adjusting pot go open then the current limiting go for a loop! I had lost a number of circuits die to this fault. What did is I fitted a pre regulator circuit with the bias set the current limiting. If something go amiss then the power to the voltage stage get cut off and no smoke signals.
    Did you know that electronics work with smoke? If the smoke comes out then they stop working!!

  • Murad Uddin


  • Brian

    Is this power supply available in a kit form

  • Mihai

    The reference voltage is set by P2(47k), not P1. In series with P2 must be a resistor which sets the maximum current of 1Amp(as stated in the description). Otherwise, there will be no protection when the wiper of P1 is near emitter of T3. R7 should be 2Watt, at least, for 1Amp. A simple LM336-(5) as a reference voltage yields much better results than CA3086 as volt. ref.

    QUOTE: “Once potentiometer P1 is set at maximum, current limiting is disabled.”

    What is the point of this? To burnout the series regulator?

  • menard

    can you provide a power supply circuit for a cheap ordinary laser pointer. I have already damaged 2 laser pointers due to inappropriate current. I used 2x 100 ohm 1 watt resistors to limit the current from the 5.3 voltage source of PSU. I have measured the current of the original (battery source) circuit, which is equivalent to 23mA, which whn I calculated, I need 196 ohms to limit the current. Is this correct? if so why did the laser did not brightly lit? it did lase but too small point only (not bright as using button cell batteries. I tried to decrease the resistance by using 50 ohms but still the same. I would be appreaciative if someone can provide me a circuit schematic. I intend to use this circuit as a laser fence for my house and dream farmland