This is a Variable 5 to 20V DC Supply Circuit Diagram . If you are looking for a low drop voltage regulator that can provide a power supply of 1A with an output voltage of between 5V and 20V DC, National Semiconductor LM2941 Low Dropout Adjustable Regulator is that you can pick to make use of. It's a typical dropout voltage of 0.5V which means that the input supply need only must be 0.5V DC over the desired output voltage. Variable 5 to 20V DC Supply Circuit Diagram Its other features include internal short circuit current limit and reverse battery protection. As shown in the schematic below, the regulator has five pins which consists of the ON/OFF control, Input Voltage, Output Voltage, Ground & Adjustable pins. ON/OFF is used for the purpose of switching on & off of the regulator. The capacitors C1 & E1 are to be placed as close as feasible to the regulator. The output of the circuit can be varied by varying the worth of potentiometer VR1 from 5V DC to 2...