Distinguish between half-wave and full-wave rectifiers.

Half-wave rectifier: (i) The rectified output is for only half of the ac cycle. (ii) One diode is used for rectification. (iii) Secondary of the transformer supplies the input across the two terminals of a diode along with a load. (iv) The output is taken across the load connected in series with the diode. Full-wave rectifier(centre-tapped rectifier): (i) The rectified output is for the complete ac cycle i.e. positive as well as the negative half. (ii) Two diodes are used and each rectifies in the alternate half cycle. (iii) The input by the secondary of a transformer is provided at the two terminals connected to the p - side of the two diodes. (iv) The output is taken between the centre tap of the transformer and the common terminal of the n - sides of two diodes.

What is rectification? Explain the working of a full wave rectifier.

The conversion of alternating current into the direct current is called rectification. Diodes are used for rectification because they allow the unidirectional flow of current. Diodes conduct only when they are forward biased. When two diodes are used in a circuit we get the output voltage during the positive and negative half cycles of the input ac voltage. The circuit for a full-wave rectifier is shown below: For a full-wave rectifier, the secondary of a transformer is provided with a centre-tapping. The p - side of two diodes is connected to the two ends of the secondary of a transformer. The n - side of the diodes are connected together and the output is taken between the common point of diodes and the midpoint of the secondary transformer. We know that a diode conducts when it is forward biased. When A is positive, the diode D 1 conducts and when B is positive then D 2 conducts. Each diode rectifies only for half of the cycle, but the two do it for alternate half cycles. Thus, the output between their common terminal and the centre-tap of the transformer becomes a full-wave rectifier output. The input and output signal of a full-wave rectifier is shown below.

In which bias can a Zener diode be used as voltage regulator?

A zener diode is designed to operate in a breakdown region. As the reverse voltage is increased, after the reverse breakdown voltage, a large change in reverse current is possible by almost an insignificant change in reverse voltage. In other words, the zener voltage remains constant even though the current through zener diode varies over a wide range. Hence, a zener diode is always used in reverse bias for regulating supply voltages.

Draw the circuit symbols for p - n - p and n - p - n transistors.

A transistor has three doped regions forming two p - n junctions between them. Two types of junction transistors are possible. Circuit symbols for both types of transistors are shown below. The arrowhead shows the direction of the conventional current in the transistors. The circuit symbol for p - n - p transistor: (ii) Circuit symbol for n - p - n transistor:

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Draw an OR gate using two diodes and explain its operation. Write the truth table and logic symbol of OR gate.

Important Questions on Semiconductor Electronics: Materials, Devices and Simple Circuits

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Intermediate Second Year Physics>Chapter 15 - Semiconductor Electronics: Materials, Devices and Simple Circuits>MODEL QUESTIONS (IPE PATTERN)>Q 7

Sketch a basic AND circuit with two diodes and explain its operation. Explain how doping increases the conductivity in semiconductors?

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Intermediate Second Year Physics>Chapter 15 - Semiconductor Electronics: Materials, Devices and Simple Circuits>MODEL QUESTIONS (IPE PATTERN)>Q 1

In a half wave rectifier, a $p - n$ junction diode with internal resistance $20 Ω$ is used. If the load resistance of $2 kΩ$ is used in the circuit, then find the efficiency of this half wave rectifier.

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Intermediate Second Year Physics>Chapter 15 - Semiconductor Electronics: Materials, Devices and Simple Circuits>MODEL QUESTIONS (IPE PATTERN)>Q 2

A full wave p-n junction rectifier uses a load resistance of $1300 Ω$ . The internal resistance of each diode is $9 Ω$ . Find the efficiency of this full wave rectifier.

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Intermediate Second Year Physics>Chapter 15 - Semiconductor Electronics: Materials, Devices and Simple Circuits>MODEL QUESTIONS (IPE PATTERN)>Q 3

Calulate the current amplification factor $β$ (beta) when change in collector current is $1 mA$ and change in base current is $20 μA$ .

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Intermediate Second Year Physics>Chapter 15 - Semiconductor Electronics: Materials, Devices and Simple Circuits>MODEL QUESTIONS (IPE PATTERN)>Q 4

For a transistor amplifier, the collector load resistance $R_{L} = 2 kΩ$ and the input resistance $R_{i} = 1 kΩ$ . If the current gain is $50$ , calculate the voltage gain of the amplifier.

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Intermediate Second Year Physics>Chapter 15 - Semiconductor Electronics: Materials, Devices and Simple Circuits>MODEL QUESTIONS (IPE PATTERN)>Q 15.1

In a n-type silicon, which of the following statement is true:

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Intermediate Second Year Physics>Chapter 15 - Semiconductor Electronics: Materials, Devices and Simple Circuits>MODEL QUESTIONS (IPE PATTERN)>Q 15.2

Which of the statements is true for p-type semiconductors?

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Intermediate Second Year Physics>Chapter 15 - Semiconductor Electronics: Materials, Devices and Simple Circuits>MODEL QUESTIONS (IPE PATTERN)>Q 15.3

Carbon, silicon and germanium have four valence electrons each. These are characterized by valence and conduction bands separated by energy band gap respectively equal to

{(E g)}_{C}, {(E g)}_{S i}

and

{(E g)}_{G e}

. Which of the following statements is true?

Draw an OR gate using two diodes and explain its operation. Write the truth table and logic symbol of OR gate.

Important Questions on Semiconductor Electronics: Materials, Devices and Simple Circuits

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