This voltage regulator input need around 20 Volt to 25 Volt. The voltage regulator with zero ripple voltage regulator with zero fluctuations is the usual parametric stabilizer, but the inverting input of op amp is fed from the potentiometer 10 k of the voltage ripple. These voltages are summed in opposite phase. 10K potentiometer can be adjusted compensation ripple at the output of the stabilizer, to virtually zero.
