Download MBBS TMU 3rd Year 2016 MBBS301A Community Medicine I Question Paper

1. a) Explain the various compensation techniques used for transistor biasing. [7M]

   b) Design a collector to base bias circuit using silicon transistor to achieve a stability factor of 'S' ≤ 10. Given V_CC = 12V, V_BE = 0.7V, h_fe = 100, and I_C = 2mA. [7M]

   OR

   a) Explain the concept of thermal runaway and derive the condition to avoid thermal runaway. [7M]

   b) Explain the need for biasing and stabilization in transistor circuits. Discuss the factors affecting the stability of the Q-point. [7M]

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2. a) Explain the operation of common emitter amplifier using h-parameter model and derive expressions for its A_I, R_i, A_V, and R_O. [7M]

   b) For the circuit shown in Figure 1, the transistor parameters are: h_fe = 100, h_ie = 1kΩ, h_re = 2 × 10^-4, h_oe = 25µA/V. Determine A_I, R_i, A_V, and R_O. [7M]

   OR

   a) Draw the cascade configuration of amplifier and derive the expressions for voltage gain, input resistance and output resistance. [7M]

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   b) A CE amplifier is designed with the following specifications: R_S = 1kΩ, R₁ = 50kΩ, R₂ = 2kΩ, R_C = 2kΩ, R_L = 1kΩ, V_CC = 20V, h_fe = 50, h_ie = 1.1kΩ, h_re = 2.5 × 10^-4, h_oe = 24µA/V. Calculate A_I, A_V, A_VS, R_i and R_O. [7M]

3. a) Classify different types of feedback amplifiers and discuss their characteristics. [7M]

   b) An amplifier with open loop voltage gain of 1000, and feedback factor β = 0.1 is subject to gain change due to temperature. If the open loop gain changes by 10%, calculate the percentage change in closed loop gain. [7M]

   OR

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   a) Derive the expressions for input resistance, output resistance, voltage gain of voltage series feedback amplifier. [7M]

   b) Calculate the gain, input impedance, and output impedance of a voltage shunt feedback amplifier having A = -300, R_i = 1.5kΩ, R_O = 50kΩ, and β = -0.01. [7M]

4. a) Explain the Barkhausen criteria for sustained oscillations. [7M]

   b) With the help of a neat circuit diagram explain the working principle of RC phase shift oscillator and derive the expression for frequency of oscillation. [7M]

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   OR

   a) Explain the principle of operation of Colpitts oscillator with neat circuit diagram. Also, derive the expression for frequency of oscillation. [7M]

   b) In a Colpitts oscillator, C₁ = 0.2µF, C₂ = 0.02µF and L = 10µH. Find the frequency of oscillation. [7M]

5. a) With the help of equivalent circuit explain the effect of cascading single tuned amplifiers on bandwidth. [7M]

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   b) Discuss the advantages and disadvantages of stagger tuned amplifier. [7M]

   OR

   a) Explain the working principle of class B push pull amplifier. Derive the expression for its efficiency. [7M]

   b) A class A series fed amplifier is operated from V_CC = 15V. If the zero signal current is 50mA, determine the maximum possible AC power output, input power and efficiency. [7M]

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