Monday, May 4, 2009
A diode is an electrical device which allows the current to move through it in one direction easily than in other direction. The junction diode is the combination of p-type and n-type semiconductor material. The lead which is connected to the p-type material is called the anode and the lead which is connected to the n-type material is called cathode. The cathode is marked by a solid line of the diode.
Fig.1 Symbol for junction diode
When p-type of the material is connected to the positive side of the battery and n-type is connected to the negative terminal, then the current flow in the circuit. Such combination of junction diode and the battery is called forward-biased. When the polarity of the battery is reversed i.e. the p-type is connected to the negative terminal of the battery and the n-type is connected to the positive terminal, then the combination is called reversed biased. In the forward biased, holes in the p-type of the material are repelled by the positive terminal of the battery and so as by negative terminal and the electrons in the n-type material. This results in the decrease in the depletion layer and hence the current flow in the circuit. But, in case of the reverse-biased, there is increase in depletion layer and the diode blocks current. The diode is assumed to be closed switch for forward-biased and open switch for reverse-biased.
CIRCUIT DIAGRAMS: -
PROCEDURE: -
Forward biasing: -
- Connect the circuit as shown in circuit diagram.
- After connection the circuit, the power supply is varied from 0V to 2V by 0.1V.
- Then, the voltage across the resistor and diode is noted.
- Then, the circuit flowing across the diode is calculated.
Reverse biasing: -
- Connect the circuit as shown in circuit diagram.
- After connection the circuit, the power supply is varied from 0V to 20V by 1V.
- Then, the voltage across the resistor and diode is noted.
- Then, the circuit flowing across the diode is calculated.
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