In the figure we have a circuit that allows us to obtain a variable voltage of approximately 0.5 to 25 V using one of the four amplifiers available on the LM3900 and LM2900. Potentiometer P1 allows you to adjust this voltage accurately and the power supply is made from a single 30 V supply. Limitations for the output current must be observed, using a driver in cases where higher power is required.
