conduct. Hence no current passes through R L . The reverse saturation current in a diode is negligible. Since there is no voltage drop across R L , the negative half cycle of AC supply is suppressed at the output.
AC Input Diode R L V o – (a) (b) v i v o time time Figure . (a) Half wave rectifier circuit (b) Input and output waveforms - - - - - - - - Unit electronics and Communication Centre tap transformer : There is a facility to tap at halfway point in the secondary windings. This helps to measure the induced voltage from one end of the secondary to the centre point. If the centre tap point is grounded, then the voltage across the secondary will be divided into two halves.
For example, if the voltage across the secondary is V, then the voltage across one end and the centre tap point is + V and at the other end it is – V. Note . . Breakdown mechanism The reverse current or the reverse saturation current due to the minority charge carriers is small.
If the reverse bias applied to a p-n junction is increased beyond a point, the junction breaks down and the reverse current rises sharply. The voltage at which breakdown happens is called the breakdown voltage and it depends on the width of the depletion region, which in turn depends on the doping level. A normal p-n junction diode gets damaged at this point. Specially designed diodes like Zener diode can be operated at this region and can be used for the purpose of voltage regulation in circuits.
There are two mechanisms that are responsible for breakdown under increasing reverse voltage. i) Avalanche breakdown Avalanche breakdown occurs in a lightly doped junctions which have wide depletion region. When reverse bias voltage exceeds a certain value, the minority charge carriers are accelerated by reverse voltage and their kinetic energy increases. These charge carriers collide potential and M is at negative potential.
This forward biases diode D and reverse biases diode