digitally selected output Adjustable regulator circuits

A very simple adjustable regulator circuit with digitally selected output is shown above. The circuit is a just a modification of the ordinary voltage regulator using LM317. Parallel to the resistor R4, four more resistor branches each with a transistor switch is added and these resistors can be included or excluded in to the circuit by making the corresponding switching transistor ON. In simple words the output voltage will be according to the logic level of the digital inputs A, B, C and D. Logic high at terminal A will make Q1 ON and so resistor R5 will be added parallel to R4 and so on. Addition of each resistance in parallel to the R4 will reduce the effective resistance of the path and so the output voltage of the resistance will decrease in steps. The width of each step depends on the value of the resistors you choose. Resistor R4 sets the maximum output voltage and it is according to the equation V out Max = 1.25V (1 + (R4/R3)) + (Iadj x R4).Electronics Circuit Application

Electronics Circuit Application