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.