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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
Explain briefly with the help of necessary diagrams, the reverse biasing of a p-n junction diode. Also draw characteristic curves.
When a p-type impurity is doped in a semiconductor, a large number of holes are created, This does not make the semiconductor charged. But when holes diffuse from the p-side to the n-side in a p-n junction, the n-side gets positively charged. Explain.
Two identical p-n junction may be connected in series with a battery in three ways. The potential difference across the two p-n junctions are equal in
A hole diffuses from the p-side to the n-side in a p-n junction. This means that
A semiconducting device is connected in a series circuit with a battery and a resistance. A current is found to pass through the circuit. If the polarity of the battery is reversed, the current drops to almost zero. the device may be
(a) an intrinsic semiconductor
(b) a p-type semiconductor
(c) an n-type semiconductor
(d) a p-n junction
In a p-n junction, a potential barrier of 250 meV exists across the junction. A hole with a kinetic energy of 300 meV approaches the junction. Find the kinetic energy of the hole when it crosses the junction if the hole approached the junction (a) from the p-side and (b) from the n-side.
Draw the current-voltage characteristics for the device show in figure between the terminals A and B.
(Assume that the resistance of each diode is zero in forward bias and is infinity in reverse bias.)
A diode, a resistor and a 50 Hz AC source are connected in series. The number of current pulses per second through the resistor is __________ .
In a semiconductor diode, the barrier potential offers opposition to only ______.
During the formation of a p-n junction ______.
