<P> The initial step in AC to DC conversion is to send the AC current through a rectifier . The ripple voltage output is very large in this situation ; the peak - to - peak ripple voltage is equal to the peak AC voltage minus the forward voltage of the rectifier diodes . In the case of a SS silicon diode , the forward voltage is 0.7 V ; for vacuum tube rectifiers , forward voltage usually ranges between 25 and 67V ( 5R4 ) . The output voltage is a sine wave with the negative half - cycles inverted . The equation is : </P>
peak to peak ripple voltage of half wave rectifier
equal to the peak AC voltage minus the forward voltage of the rectifier diodes