Circuit Components

Introduction

Circuit Components — diodes, transistors, vacuum tubes, and resistors

What is an Active Device? (B-004)

Active Device — electrically controls charge flow; one signal controls another
Passive Components — cannot increase signal power
Semiconductors — conductivity between conductors and insulators
Active Device Examples — diodes, transistors, vacuum tubes, and integrated circuits
Component Categories — passive versus active components

Amplifiers — Signal Gain (B-004-001)

Amplifier — a circuit designed to increase signal amplitude
Amplifier Types — RF amplifier for antenna signals, audio amplifier for microphone signals
Non-linear Amplifier — causes distortion, spurious emissions, and harmonics

Semiconductor Diode — One-Way Current Flow (B-004-002)

Diode — two electrodes: anode and cathode with one-way current flow
Diode Applications — rectification, detection, reverse polarity protection, and voltage spike suppression
Zener Diode — operates in reverse breakdown for voltage regulation

Zener Diodes — Voltage Regulation (B-004-002, B-004-003)

Zener Diode Operation — designed to operate in reverse breakdown reliably and non-destructively
Zener Purpose — regulate or maintain a constant voltage across a load
Zener Applications — voltage regulation, reference voltage, overvoltage protection

Bipolar Junction Transistor (BJT) (B-004-003)

Bipolar Junction Transistor — two PN junctions with three electrodes: collector, emitter, and base
BJT Operating States — active for amplification, saturation fully on, cut-off fully off

Field Effect Transistor (FET) (B-004-004)

FET Electrodes — gate, drain, and source with N-channel and P-channel types
FET versus BJT — voltage-controlled versus current-controlled

Vacuum Tubes — Triode (B-004-005)

Triode — three-electrode vacuum tube: cathode, grid, and plate
Grid Control — electron flow controlled like base in BJT or gate in FET

Device Comparison — BJT, FET, Triode (B-004-003, B-004-004, B-004-005)

Device Comparison — control electrode, output electrodes, control method, and impedance
Control Method Difference — BJT is current-controlled; FET and triode are voltage-controlled
Practical Considerations — power handling, frequency response, and voltage requirements

Resistor Colour Codes — 4-Band System (B-004-006)

Four-band Resistor Code — bands one and two are digits, band three is multiplier, band four is tolerance
Resistor Precision — tolerance and temperature coefficient of resistors

Resistor Tolerance and Temperature (B-004-006)

Resistor Tolerance — how much actual resistance may vary from nominal value
Temperature Coefficient — how resistance changes with temperature

Chapter 4 — Key Takeaways

Active Devices — control charge flow and amplify, unlike passive components
Diode and Zener — one-way anode-to-cathode conduction; Zener uses reverse breakdown for regulation
BJT and FET — base current controls BJT; gate voltage controls FET
Triode — grid voltage controls cathode-to-plate electron flow; used for high-power RF
Resistor Colour Code — first two bands are digits, third is multiplier, fourth is tolerance