Capacitor Basics and Applications Quiz

Module 4: Semiconductor Devices

• Covers the evolution of electronics, from vacuum tubes to nanoelectronics.
• Includes details on resistors, capacitors, and inductors, including types, specifications, and color coding.
• Discusses PN junction diodes, explaining their principle of operation, V-I characteristics, and avalanche breakdown.
• Explores bipolar junction transistors (BJTs), detailing PNP and NPN structures, principles of operation, and relationships between current gains (CE, CB, CC).
• Includes input and output characteristics of common emitter configurations.

Capacitor

• Used for storing electrical charge.
• Constructed from two metal plates separated by a dielectric medium.
• Capacitance measures the amount of charge stored.
• Farad (F) is the SI unit of capacitance.
• Other units include µF, nF, and pF.

Capacitor Behavior

• When connected to a battery, a capacitor charges.
• When the battery is removed, it discharges.
• Capacitors allow AC signals to pass but block DC signals.
• In series circuits, they block DC signals from flowing between circuits while allowing AC signals to pass through.
• In shunt circuits, they pass AC signals without allowing them to flow between circuits.
• Used for signal generation, tuning, timing, and filtering.

Capacitor Calculation

• Capacitance (C) is calculated by dividing the charge (Q) by the voltage (V): C = Q/V.
• The equation C = ε₀A/d describes capacitance, where:
• A is the area of the plates.
• ε₀ is the permittivity of the dielectric.
• d is the distance between the plates.

Capacitor Types

• Fixed Capacitors:

• Electrolytic: Used for large capacitance values; have a polarized nature (require correct DC polarity) with ranges from 1µF to 47,000µF and voltage ranges from 1V to 500V; used in filter circuits and coupling.

• Ceramic: Non-polarized capacitors, range from 1pF to 0.22µF and are used in high-frequency applications.

• Mica: Non-polarized capacitors with mica dielectric; used in resonance circuits and ripple filtering in power supply circuits; have range from 5 to 10,000pF and voltages up to 500V.

• Paper: Oil-impregnated paper is used as a dielectric between aluminum foils in film style capacitors; are non-polarized; have disadvantages of large size; range from 300pF to 4 µF and voltage ranges from 600V.

• Variable Capacitors: Variable capacitance based on requirement; used for tuning.

• Gang Capacitor: A group of capacitors connected together on a shaft to adjust capacitance for tuning.

• Trimmer: Used when adjusting capacitance value is not frequent; two plates mounted on a base, separated by a dielectric material, adjustable using a screw.

Capacitor Numbering System

• Values greater than 1 are given in pF.
• Values less than 1 are given in µF.
• Three-digit numbers imply the first two digits are the values and the third represents the number of zeros added to the first two. 
• Letter "k" signifies kilo-prefix (e.g., "10k" means 10kpF.).
• A letter "n" or "M" indicates nano or micro farads, respectively.
• Example: "473J" = 47,000 pF (or 47nF), or ±5% tolerance.

Capacitor Color Coding

• Capacitors use color bands for identifying capacitance value.
• Reading bands from left to right:
• First band: first digit.
• Second band: second digit.
• Third band: multiplier (number of zeros).
• Fourth band (some): tolerance (percentage).
• Fifth band (some): temperature coefficient.
• Sixth band (some): working voltage.