SEMICONDUCTOR ELECTRONICS
Very Short Question Answers
Q1. What is an n-type semiconductor? What are the majority and minority charge carriers in it?
Ans.n-type semiconductor: Germanium or silicon doped with pentavalent impurity like arsenic is called n- type semiconductor.Majority charge carriers: electrons
Minority charge carriers: holes.
Q2. What are intrinsic and extrinsic semiconductors?
Ans.Intrinsic semiconductor: Pure semiconductor like silicon is called intrinsic semiconductor.
Extrinsic semiconductor: A semiconductor doped with trivalent or pentavalent impurity is called extrinsic semiconductor.
Q3. What is a p-type semiconductor? What are the majority and minority charge carries in it?
Ans.p-type semiconductor: Germanium or silicon doped with trivalent impurity like indium is called p-type semiconductor.Majority charge carriers: holes
Minority charge carriers: electrons.
Q4. What is p-n unction diode? Define depletion layer?
Ans.p-n junction diode: An arrangement consisting of p-type semiconductor brought in close contact with n-type semiconductor is called p-n junction diode
Depletion layer: The region near the p-n junction which is free from mobile charge carriers is called depletion layer.
Q5. How is a battery connected to a junction diode in i) forward bias and ii) reverse bias?
Ans.Forward bias: In forward bias, the p-side of diode is connected to positive terminal of battery and n-side connected to negative terminal of battery.
Reverse bias: In reverse bias, the p-side of diode is connected to negative terminal of battery and n –side connected to positive terminal of battery.
Q6. What is the maximum percentage of rectification in half wave and full wave rectifiers?
Ans.Maximum percentage of rectification in half wave rectifier is 40.6 %. Maximum percentage of rectification in full wave rectifier is 81.2%.
Q7. What is Zener voltage and how will a Zener diode be connected in circuits generally?
Ans.Zener voltage: The reverse bias voltage of Zener diode, at which current increase suddenly is called Zener voltage. Zener diode is connected in reverse bias.
Q8. Write Expressions for the efficiency of a full wave rectifier and a half wave rectifier?
Ans. Efficiency of full wave rectifier $\eta =\frac{0.812\times \, R_{L}}{r
_{f}+R_{L}}$
Efficiency of half wave rectifier $\eta =\frac{0.406\times \, R_{L}}{r
_{f}+R_{L}}$
Q9. What happens to the width of the depletion layer in a p-n junction diode? When it is i) forward biased and ii)reverse biased?
Ans.In forward bias the width of depletion layer of a diode decreases.
In reverse bias, the width of depletion layer of a diode increases
Q10. Draw the circuit symbols for p-n-p and n-p-n transistors?
Ans. 
Q11. Define amplifier and amplification factor
Ans.Amplifier: The process of raising the strength of a signal is called amplification.
The device used to do amplification is called amplifier.
Amplification factor(A): The ratio of output voltage to input voltage is called amplification factor $ A=\frac{V_{\circ}}{V_{i}} $
Q12. In which bias can a Zener diode be used as voltage regulator?
Ans.Reverse bias.
Q13. Which gates are called universal gates?
Ans.NAND and NOR gates.
Q14. Write the truth table of NAND gate. How does it differ from AND gate?
Ans. NAND gate truth table
| $A$ | $B$ | $Y= \overline{A.B}$ |
| $0$ | $0$ | $1$ |
| $0$ | $1$ | $1$ |
| $1$ | $0$ | $1$ |
| $1$ | $1$ | $0$ |
The output of NAND gate is an inversion of AND gate.
Short Question Answers
Q1. What are n-type and p-type semiconductors? How is a semiconductor Junction formed?
Q2. Discuss the behavior of p-n junction. How does a potential barrier develop at the junction?
Q3. Draw and explain the current-voltage (I-V) characteristic curves of a junction diode in forward and reverse blas.
Q4. Describe how a semi conductor diode is used as a half wave rectifier.
Q5. What is rectification? Explain the working of a full wave rectifier.
Q6. Distinguish between half-wave and full-wave rectifiers..
Q7. Distinguish between zener breakdown and avalanche breakdown.
Q8. Explain hole conduction in intrinsic semiconductors.
Q9. What is a photodiode? Explain its working with a circuit diagram and draw its I-V characteristics..
Q10. Explain the working of LED and what are its advantages over conventional incandescent low power lamps.
Q11. Explain the working of a solar cell and draw its I-V characteristics.
Q12. Explain the different transistor configurations with diagrams.
Q13. Explain how transistor can be used as a switch?
Q14. Explain how transistor can be used as an oscillator?
Q15. Define NAND and NOR gates. Give their truth tables.
Q16. Explain the operation of a NOT gate and give its truth table.
Long Question Answers
Q1. What is a junction diode?Explain the formation of depletion region at the junction Explain the variation of depletion region in forward and reverse-biased condition.
Q2. What is a rectifier? Explain the working of half wave and full wave rectifiers with diagrams.
Q3. What is a Zener diode?Explain how it is used as a voltage regulator.
Q4. Describe a transistor and explain its working. What is amplification?
Q5. Explain the working of a common emitter amplifier with necessary diagram..
Q6. Draw an OR gate using two diodes and explain its operation.Write the truth table and logic symbol of OR gate.
Q7. Sketch a basic AND circuit with two diodes and explain its operation. Explain how doping increases the conductivity in semiconductors?
Problems Question Answers
Q1. In a half wave rectifier, a p-n junction diode with internal resistance 20 ohm is used. If the load resistance of 2 ohm is used in the circuit ,then find the efficiency of this half wave rectifier.
Q2. A full wave p-n junction diode rectifier uses a load resistance of 1300 ohm The internal resistance of each diode is 9 ohm .Find the efficiency of this full wave rectifier.
Q3. Calculate the current amplification factor B(beta) when change in collector current is ImA and change in base current is 20uA.
Q4. For a transistor amplifier, the collector load resistance R-2k ohm and the input resistance R=1 K ohm. If the current gain is 50. calculate voltage gain of the amplifier.