IEC MOD 4 QB UPTO ST1

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Introduction to Electronics Engineering

• Module 4 Question Bank

  • Key topics include active vs passive components and color coding of resistors.

Active and Passive Components

• Active Components: Components that require energy input; can control current flow (e.g., transistors, diodes).

• Passive Components: Components that do not require energy to operate; they dissipate energy (e.g., resistors, capacitors).

Color Coding of Resistors

• Used for indicating values or ratings of resistors.

• Four Color Bands:

  • First Band: Most significant figure.

  • Second Band: Second significant figure.

  • Third Band: Multiplier (indicates number of zeros).

  • Fourth Band: Tolerance on resistance value.

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Example of Color Coding

• Example Bands: Grey, Blue, Gold, Gold.

  • Resistance Calculation:

    • Resistance Value: 8.6Ω±5%

    • 5% of 8.6Ω = 0.43Ω

    • Minimum Value = 8.6 - 0.43 = 8.17Ω

    • Maximum Value = 8.6 + 0.43 = 9.03Ω

PN Junction Diode

• Formed by joining P-type and N-type semiconductors (two terminals: Anode from P-type, Cathode from N-type).

• Forward Bias Condition:

  • Anode positive, Cathode negative.

  • Reduction in depletion region width; diode conducts current beyond a specific voltage threshold.

  • Breakover Voltages: Silicon = 0.7V, Germanium = 0.3V.

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Reverse Bias Condition

• Diode connected in reverse bias:

  • Increases width of the depletion region, preventing current flow except a small leakage (reverse saturation current).

  • At reverse breakdown voltage, significant current flows due to electron-hole pair generation (avalanche breakdown).

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Characteristics of a PN Junction Diode

• Forward Characteristics:

  • Current is initially small; increases sharply after overcoming barrier potential at around 0.7V (for silicon).

  • Knee Voltage (Vo): 0.7V (Si), 0.3V (Ge).

Reverse Characteristics

• Current remains relatively constant and minimal until breakdown\v.

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Avalanche Breakdown

• Rapid increase in reverse current due to carrier multiplication caused by high-energy collisions, resulting in large current flow.

Zener Diode

• Specially designed diode for breakdown operation in reverse bias, producing a constant reverse voltage. It is used primarily for voltage regulation.

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Application as Voltage Regulator

• In circuits, the Zener diode regulates voltage across the load by causing breakdown when input exceeds Zener voltage.

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Rectifiers Overview

• Function: Convert AC to DC (using diodes).

• Types:

  • Half Wave Rectifier: Uses one diode to conduct only one half of AC signal.

  • Full Wave Rectifier: Uses multiple diodes (either center tapped or bridge rectifier).

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Half Wave Rectifier

• Converts AC signal to DC by allowing only one cycle.

• Efficiency: Approximately 40.5%.

Components

• Consists of a diode, transformer, and resistive load.

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Operational Characteristics

• During positive cycle: diode conducts; during negative cycle: diode blocks current flow.

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Center-Tap Full Wave Rectifier

• Utilizes two diodes connected to a center-tapped transformer.

• Conducts both halves of AC cycles to produce DC.

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Full Wave Bridge Rectifier

• Uses four diodes to rectify AC without needing a center-tapped transformer.

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Peak Inverse Voltage (PIV)

• Maximum reverse voltage; significant for preventing diode damage.

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Ripple Factor

• Measuring unwanted AC component after rectification.

  • Calculations: For half and full wave rectifiers.

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Working with Capacitor Filter

• Capacitor maintains voltage across the load by charging and discharging as the rectified wave fluctuates.

• Useful for smoothing output.

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Rectifier Types with Capacitor Filters

• Illustrates voltage stabilization with various configurations.

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Transistor Construction

• Components: Emitter, Base, Collector.

• NPN and PNP configurations differ in charge carriers.

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NPN Transistor Operation

• Forward bias at E-B junction allows electron flow, contributing to collector current predominantly.

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Input-Output Characteristics of BJT

• Input: Analyzing base current against base-emitter voltage.

• Output: Evaluating collector current with constant input current.

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Current Amplification Factor

• Expression for amplification in various transistor configurations.