JNTU
JNTU B.Tech II ANALOG ELECTRONICS Previous Question Paper (March - 2022 - R18)
Answer any five questions. All questions carry equal marks.
Main
How does the reverse saturation current of a diode and voltage varies with temperature? Explain.
Answer
The reverse saturation current (Io) of a diode is highly temperature-dependent. It approximately doubles for every 10°C rise in temperature for both Germanium and Silicon diodes. This occurs because the number of minority charge carriers generated due to thermal energy increases exponentially with temperature.
The forward voltage drop (Vf) across a diode decreases as temperature increases. For a constant forward current, the voltage drop decreases by approximately 2 mV per degree Celsius (2 mV/°C). This happens because the thermal voltage (VT = kT/q) increases with temperature, which reduces the potential barrier required to maintain the same level of diffusion current.
Derive the expressions for the following parameters of the half wave rectifier circuit:
- Average DC current
- RMS value of current
- Rectifier efficiency
Answer
For a half-wave rectifier with input voltage v = Vm sin(ωt) and load resistance RL, the current is i = Im sin(ωt) for 0 ≤ ωt ≤ π, where Im = Vm / (Rf + RL).
1. Average DC Current (Idc):
2. RMS Value of Current (Irms):
3. Rectifier Efficiency (η):
Efficiency is defined as the ratio of DC output power to AC input power. The DC output power is Pdc = Idc2RL and the AC input power is Pac = Irms2(Rf + RL).
Assuming an ideal diode where Rf = 0, the maximum theoretical efficiency is 4 / π2, which is approximately 40.6%.
Discuss the self bias circuit and derive the expression for S?
Answer
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Explain the drain characteristics of depletion MOSFET.
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Explain the small signal model of CS MOSFET amplifier. Also derive the expression for amplification factor.
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Write short note on MOSFET as a resistor.
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Explain the working of common emitter direct coupled amplifier.
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Prove that class B push pull amplifier efficiency is 78.5%.
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Derive the voltage gain for unbalanced output differential amplifier.
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Explain the operation direct coupled class-A power amplifier.
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Draw the circuit of current series feedback amplifier and derive the expressions for input and output resistances.
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Why are RC oscillators preferred for the generation of low frequencies?
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Calculate the gain, input impedance and output impedance of voltage series feedback amplifier having A = -300, Ri = 50KΩ and β = -1/20.
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Explain non inverting op-amp circuit.
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Construct an op-amp integrator circuit to and explain.
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Explain differential amplifier using one op-amp.
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