BU Sem-5-PHYS-5013 Question - 2025
Physics of Semiconducting Materials: Classification of metals, conductors and semiconductors (a) on the basis conductivity, (b) on the basis of energy bands, Elemental and compound semiconductors with examples, Intrinsic semiconductors – electrons and holes as charge carriers, Extrinsic semiconductors - doping and dopants, n- type and p- type semiconductors, p-n junction – diffusion current and drift current, Depletion region, Barrier potential, Semiconductor diode - p-n junction diode under forward bias, p-n junction diode under reverse bias, V-I characteristics of a p-n junction diode (a) in forward bias, (b) in reverse bias, Ideal diode equation.
Different Diodes and their Applications:
Standard silicon diode: Rectification and rectifiers - half-wave, full-wave rectifiers (centretapped and bridge), ripple factor and rectification efficiency. Zener diode: Voltage regulation.
Light emitting diode (LED): Displays indicators, and other lighting applications.
Schottky diode: Fast switching speed suitable for high-frequency applications.
Photodiode: Optical communications, light detection in remote controls, and medical instruments.
Tunnel diode: High-speed switching, high-frequency oscillators, and applications requiring fast switching and low power consumption.
Bipolar Junction Transistor (BJT): Structure - n-p-n and p-n-p transistors, Physical construction- emitter, base, collector and doping characteristics, BJT biasing Characteristics of CB, CE and CC configurations, Current gains α and β and relations between α and β, Load line analysis of transistors, DC Load line and Q-point, Concept of biasing, Active, cut-off and saturation regions.
BJT Biasing: Biasing Techniques: Exploration of fixed bias, collector-to-base bias, and voltage divider bias, Advantages and disadvantages of each biasing.
BJT Amplifiers: Configurations: Study of common-emitter, common-collector, and common-base amplifier configurations, their advantages, and disadvantages, Amplifier Analysis: Analyzing small-signal equivalent circuits, Calculating voltage and current gain, input and output impedances, Coupled Amplifier: RC coupled amplifier, Frequency response and gain band width product.
Feedback in Amplifiers: Concepts of feedback and the effects of positive and negative feedback on amplifier performance: Input Impedance, Output Impedance, Gain, Stability, Distortion and Noise.
(4 Lectures)
Sinusoidal Oscillators: Understanding the principles of oscillation, Barkhausen's Criterion for self-sustained oscillations, Common Oscillator Circuits: RC phase shift oscillator, Wien Bridge oscillator, Hartley oscillator and Colpitts oscillator.
Modulation and Demodulation: Need for modulation in communication systems, Basic components of a communication system (transmitter, channel, receiver), Understanding the concept of carrying information using a carrier wave, Amplitude Modulation (AM): Definition and principle of AM, Time domain and frequency domain representation of AM signals, Power relations in AM waves, Modulation index and its significance, Generation and detection of AM waves using various techniques like square law modulator, switching modulator, and envelop detection, Frequency Modulation (FM) : Definition and principle of FM, Mathematical analysis of FM and PM.
Operational Amplifiers: (Black Box approach) Characteristics of an ideal and practical op-amp, (IC 741), Open-loop and Closed-loop gain, Frequency response, CMRR, Slew rate and concept of virtual ground.
Applications of Op-Amps: (1) Inverting and non-inverting amplifiers, (2) Adder, (3) Subtractor, (4) Differentiator, (5) Integrator, (6) Log amplifier, (7) Zero crossing detector (8) Wein bridge oscillator.
A/D Conversion: Resistive network, (weighted and R-2R ladder), Accuracy and resolution, A/D Conversion (successive approximation).