BASIC ELECTRONICS

BASIC ELECTRONICS
SEM-I, 2010-11
B TECH QUESTION PAPERS
UTTARAKHAND TECHNICAL UNIVERSITY
(UTU)

Time: 3 Hours

Total Marks: 100

Note: Attempt all questions

Attempt any four parts of the following:

1. Draw the simplified energy level diagram of a solid.
2. On the basis of energy band gap theory, explain the formation of valence band. Differentiate among conductors, insulators and semiconductors.
3. Define the term conductivity, intrinsic concentration and energy gap of semiconductors.
4. The mobilities of free electrons and holes in a pure germanium are 0.38 and 0.18 m2/V-s. Find the value of intrinsic conductivity. Assume n =2.5 x 10¹⁹/m³ at room temperature.
5. A sample of silicon is doped with phosphorous to a density of 10²¹/m³ as well as Boron to a density of 5 x 10²⁰/m³. What will be conductivity of the Si sample? The electron mobility in silicon is 0.18 m²/V-s.

Attempt any four parts of the following:

1. Define the following terms
   (i) knee voltage
   (ii) Peak Inverse voltage
   (iii) Breakdown voltage
2. Explain the break mechanism which occurs in zener diode.
3. For a semiconductor diode, define static and dynamic resistance.
4. What is the basic difference between the clipper and clamper circuit.
5. Distinguish between zener breakdown and avalanche breakdown.

Attempt any two parts of the following:

1. What is clipping circuits? Draw the output waveform for positive and negative clipper if the input is sinusoidal. Also explain the operation of combinational clipper for a square input.
2. Draw the V-I characteristics of a zener diode and explain how does a zener regulate a voltage. The input voltage for the figure shown below varies from 35 to 45 volt, V_z = 20 V, r_z = 5 ohm, I_L(min) = 0 mA, I_L(max) = 10 mA, I_Z(max) = 400 mA, Find the value of R_L, R and P_Z(max).
   
3. Draw and explain the input and output characteristics of a BJT in CE configuration, indicating the operating regions. Derive the relationship between α, β and γ. Explain why CE configuration most widely used amplifier circuits.

Attempt any two parts of the following:

1. Determine pinch off voltage, amplification voltage and drain resistance of FET. Explain the volt ampere characteristics of FET. Using suitable circuit arrangement derive the relationship μ = r_d x g_m.
2. What is significant difference between the construction of an enhancement type MOSFET and depletion type MOSFET. Explain with suitable diagram.
3. Differentiate among BJT and FET. What are the advantages of the FET over a conventional BJT.

Attempt any two parts of the following:

1. Draw the ac equivalent circuit of a common source amplifier, and find the expression for the voltage gain.
2. Perform the following conversion
   (i) (1BE)₆ = ( )₈
   (ii) (676)₈ = ( )₂
   (iii) (321)₄ = ( )₁₀
   (iv) (10101.001)₂ = ( )₈
3. Minimize the following Boolean function using K-map.
   
   
   Also find the POS form the above simplified Boolean expressions.

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