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प्रश्न
How is a zener diode fabricated so as to make it a special purpose diode? Draw I-V characteristics of zener diode and explain the significance of breakdown voltage.
Explain briefly, with the help of a circuit diagram, how a p-n junction diode works as a half wave rectifier.
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उत्तर
Zener is fabricated such that both the p-type and the n-type are highly doped. This makes the depletion region thin. When an electric field is applied, a high electric field appears across the thin depletion region. When the electric field becomes very high, it knocks off electrons from the host atoms to create a large number of electrons. This results in a large value of current inside the circuit.
Zener has a sharp breakdown voltage and this property of zener is used for voltage regulation.
An ac current has a positive half cycle and a negative half cycle. A pn junction allows current to pass only in one direction and that is when it is forward biased.
When a positive half-cycle occurs, the p-side has a lower potential. Therefore, the diode is now forward biased and therefore conducts and this positive cycle is available for the load.
When a negative half cycle occurs, the n-side has a higher potential than the p-side. Hence, the diode is now reverse biased and thus, does not conduct. As a result, this positive half cycle also does not conduct. Therefore, it does not appear at the load and is cut-off.
We obtain a waveform, which has only positive half cycles and therefore it is called half-wave rectifier.
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संबंधित प्रश्न
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I = `"I"_0 exp ("eV"/(2"k"_"BT") - 1)`
where I0 is called the reverse saturation current, V is the voltage across the diode and is positive for forward bias and negative for reverse bias, and I is the current through the diode, kBis the Boltzmann constant (8.6×10−5 eV/K) and T is the absolute temperature. If for a given diode I0 = 5 × 10−12 A and T = 300 K, then
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