D . Hence, being forward biased, diode D conducts and current flows along the path ND ABC During both postive and negative half cycles of the input signal, the current flows through the load in the same direction. The output signal corresponding to the input signal is shown in Figure . (b).
Though both half cycles of AC input are rectified, the output is still pulsating in nature. The efficiency (η) of full wave rectifier is twice that of a half wave rectifier and is found to be . %. It is because of power losses in the winding, the diode and the load resistance.
M N R L – D D Current flow during positive half cycle Current flow during negative half cycle (a) C AC Input V o (b) v i v o time time Figure . (a) Full wave rectifier circuit (b) Input and output waveforms - - - - - - - - Unit electronics and Communication . . Zener diode Zener diode is a heavily doped silicon diode used in reverse biased condition and is named after its inventor Clarence Melvin Zener.
It is specially designed to be operated in the breakdown region. The doping level of the silicon diode can be varied to have a wide range of breakdown voltages from V to over V. As explained in the previous section, Zener breakdown occurs due to the breaking up of covalent bonds by the strong electric field set up in the depletion region by the reverse voltage. It produces an extremely large number of electrons and holes which constitute the reverse saturation current.
The current is limited by both external resistance and power dissipation of the diode. A Zener diode is shown in Figure . (a) and its circuit symbol is given in Figure . (b).
It looks like an ordinary p-n junction diode except that n -side lead resembles the shape of the letter ‘z’. The arrow head points the direction of conventional current. In Figure . (a), black ring indicates the n -side lead.