The filter capacitor converts the fullwave rippled output of the rectifier into a
smoother DC output voltage. Generally for DC power supply circuits the filter
capacitor is an aluminium electrolytic type that has a capacitance value of 100 μF or more with repeated DC
voltage pulses from the rectifier charging up the capacitor to peak voltage. However, there
are two important parameters to consider when choosing a
suitable filter capacitor and these
are its Working Voltage, which must be higher than the no load output value of the rectifier and its Capacitance Value, which determines the amount of ripple that will appear superimposed on top of the DC voltage