Q. What is rectification? How can a diode valve be used as half wave rectifier and full wave rectifier?
Q. Explain how the depletion layer and the barrier potential are formed in a p-n junction diode. 
Q. Draw a circuit diagram for use of NPN transistor as an amplifier in common emitter configuration. The input resistance of a transistor is 1000 ohm. On changing its base current by, 10$\mu$A the collector current increases by 2 m A.
If a load resistance of 5K ohm is used in the circuit, calculate (i) the current gain & (ii) voltage gain of the amplifier.
Q. The output of an AND gate is connected to both the inputs a NAND gate.  Draw logic circuit of this combination of gates and write its truth table. 
Q. What is a Zener diode? How it is symbolically represented? With the help of a circuit diagram, explain the use Of Zener diode as a voltage stabiliser. 
Q. With the help Of a suitable diagram. explain the formation of depletion region in a p-n junction. How does its width change when the junction is (i) forward biased? & (ii) reverse biased? 
 

1) A half wave rectifier is a special case of a clipper. In half wave rectification, either the positive or negative half of the AC wave is passed easily, while the other half is blocked, depending on the polarity of the rectifier. Because only one half of the input waveform reaches the output, it is very inefficient if used for power transfer. Half-wave rectification can be achieved with a single diode in a one phase supply. In half wave rectification, either the positive or negative half of the AC wave is passed, while the other half is blocked. Because only one half of the input waveform reaches the output, it is very inefficient if used for power transfer. Half-wave rectification can be achieved with a single diode in a one phase supply, or with three diodes in a three-phase supply. In half wave rectifier, only one diode is there. The diode will be forward biased in the positive half cycle and reverse biased in the negative half cycle. So the output will be available only during the positive half cycle and the output will be unidirectional.  

2)A full-wave rectifier converts the whole of the input waveform to one of constant polarity (positive or negative) at its output. Full-wave rectification converts both polarities of the input waveform to DC (direct current), and is more efficient. However, in a circuit with a non-center tapped transformer, four diodes are required instead of the one needed for half-wave rectification. (See semiconductors, diode). Four rectifiers arranged this way are called a diode bridge or bridge rectifier:For single-phase AC, if the transformer is center-tapped, then two diodes back-to-back (i.e. anodes-to-anode or cathode-to-cathode) form a full-wave rectifier (in this case, the voltage is half of that for the non-tapped bridge circuit above, and the diagram voltages are not to scale). In a full wave rectifier during each half cycle, one of the diodes will be forward biased and output will be available across the load resistor. So we get continuous dc output throughout the cycle.


kindly post other queries in separate thread.

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