Assignment 2 (EC for ME ME102)
(Course Instructor: Piyush Tewari, ECE, DTU)
MM:100
1. Explain the construction of an NPN and PNP BJT. Draw the schematic symbols for
both types. [CO 1] [L2] [4]
2. Describe the basic operation of a BJT in the active region. How do majority and
minority carriers contribute to the current flow? [CO 1] [L2] [4]
3. What are the three regions of operation in a BJT? Explain the conditions required for
each region. [CO 1] [L2] [4]
4. Compare the input and output characteristics of a BJT in the Common Emitter (CE)
and Common Base (CB) configurations. [CO 1] [L4] [4]
5. Why is the Common Emitter (CE) configuration the most widely used in amplifier
circuits? Explain with relevant characteristics. [CO 1] [L2] [4]
6. What is the purpose of DC biasing in a BJT amplifier? Explain the concept of the
operating point (Q-point). [CO 1] [L2] [4]
7. Draw the load line for a BJT amplifier circuit. How is the Q-point determined using the
load line? [CO 1] [L3] [4]
8. Explain the significance of the Q-point in ensuring proper amplification without
distortion. [CO 1] [L2] [4]
9. What are the disadvantages of the fixed-bias circuit? How does the voltage divider bias
circuit overcome these limitations? [CO 1] [L4] [4]
10. Compare the stability of the Q-point in fixed-bias and voltage divider bias circuits. [CO
1] [L4] [4]
11. What is the role of feedback resistors in voltage divider bias circuits? How do they
improve stability? [CO 1] [L2] [4]
12. Explain the concept of thermal runaway in BJTs. How can it be prevented in biasing
circuits? [CO 1] [L2] [4]
13. What is the significance of the Early effect in BJTs? How does it affect the output
characteristics? [CO 1] [L2] [4]
14. Compare the construction and operation of Depletion-Type MOSFET and
Enhancement-Type MOSFET. Draw their schematic symbol and transfer
characteristics. [CO 1] [L4] [4]
15. Draw the output characteristics 𝐼𝐷 vs 𝑉𝐷𝑆 of an Enhancement-Type MOSFET. Explain
the significance of the ohmic, saturation, and cutoff regions. [CO 1] [L3] [4]
16. What is the significance of the threshold voltage 𝑉𝑇𝐻 in an Enhancement-Type
MOSFET? How does it affect the biasing? [CO 1] [L2] [4]
17. What is the hybrid-pi model of a BJT? Draw the small-signal equivalent circuit and
explain the significance of each component. [CO 2] [L3] [4]
18. Define transconductance 𝑔𝑚 and small-signal input resistance 𝑟𝜋 . How are they related
to the DC bias conditions of the BJT? [CO 2] [L2] [4]
19. Derive the expressions for voltage gain 𝐴𝑣 , input impedance 𝑍𝑖𝑛 , and output impedance
𝑍𝑜𝑢𝑡 of a CE amplifier using the hybrid-pi model. [CO 2] [L3] [4]
20. Illustrate the effect of the bypass capacitor 𝐶𝐸 on the voltage gain of a npn CE BJT
amplifier. [CO 2] [L4] [4]
21. For a fixed-bias BJT circuit,𝑅𝐵 = 470 𝑘Ω , 𝑅𝐶 = 2.2 𝑘Ω , 𝛽 = 150, and 𝑉𝐶𝐶 = 12 𝑉 .
Calculate 𝐼𝐵 , 𝐼𝐶 and 𝑉𝐶𝐸 . [CO 2] [L3] [4]
22. For a voltage divider bias circuit, 𝑅1 = 10 , 𝑅2 = 2.2 𝑘Ω, 𝑅𝐶 = 3.3 𝑘Ω, 𝑅𝐸 =
1 𝑘Ω, 𝛽 = 200 and 𝑉𝐶𝐶 = 15 𝑉 . Calculate 𝐼𝐵 , 𝐼𝐶 and 𝑉𝐶𝐸 . [CO 2] [L3] [4]
23. A CE amplifier has the following parameters: 𝑅𝐶 = 4.7 𝑘Ω , 𝑅𝐸 = 1 𝑘Ω , 𝛽 = 100,
and 𝑉𝐶𝐶 = 12 𝑉 . Calculate the voltage gain and input impedance. [CO 2] [L3] [4]
24. A CE amplifier has 𝑅𝐶 = 3.3 𝑘Ω , 𝑅𝐸 = 1 𝑘Ω , 𝑔𝑚 = 50 𝑚𝑆, and 𝑟𝜋 = 2.5 𝑘Ω .
Calculate the voltage gain and input impedance if the emitter resistor is bypassed by a
capacitor. [CO 2] [L3] [4]
25. Illustrate the significance of the Early effect in the hybrid-pi model. How is it
represented in the small-signal equivalent circuit?
[CO 2] [L4] [4]