Full Wave Rectification 
If the peak applied signal voltage is Vm, then for a full wave rectifier circuit(not bridge) the PIV of the diodes should be
If the peak applied signal voltage is Vm then for a bridge rectifier circuit the PIV of the diodes will be
Four ideal Si diodes [VT = 0.7V] are used in a bridge rectifier circuit which has a peak input sinusoidal signal amplitude of 5V [Vm = 5V]. The average DC voltage is