Electronic Components & Circuits
A broad reference to parts, instruments and circuit functions, explained in everyday language with labeled illustrations, examples and specification checks.
How to use this list
Open an entry to see its illustration, what it does, an example and the specifications that matter. Tap any image to enlarge it. Images are original representative illustrations, not photographs, exact pinouts or guarantees of physical identification. Component families and circuit arrangements are distinct: a capacitor is a part; a filter is a circuit that may use several parts. This reference covers common and important families, rather than every manufacturer part number or specialized circuit ever made.
Examples explain function; they are not universal replacement or wiring instructions. Appearance, package size and a matching nominal value do not establish compatibility. Stored charge, mains, vehicle batteries and high-voltage equipment require appropriate precautions and qualified procedures.
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Bridge rectifierDiodes
What it does
Combines four diode functions to obtain full-wave rectification with a defined input and output arrangement.
Example
A supply's rectification stage.
Important distinction
Rectified voltage still needs appropriate regulation or filtering when required.
Specifications to read
Forward/reverse voltage behavior, current, dissipation, recovery or response and application-specific limits.
A rating is a limit or condition, not a guarantee of suitability. Use the manufacturer's data sheet for the exact component and the equipment's schematic for its intended role.
Fast-recovery diodeDiodes
What it does
A rectifying device selected for suitable recovery behavior when switching between conduction conditions.
Example
A switching converter.
Important distinction
Recovery, thermal and voltage/current requirements must all suit the design.
Specifications to read
Forward/reverse voltage behavior, current, dissipation, recovery or response and application-specific limits.
A rating is a limit or condition, not a guarantee of suitability. Use the manufacturer's data sheet for the exact component and the equipment's schematic for its intended role.
Infrared LED and laser diodeDiodes
What it does
Emitters selected for infrared signaling or coherent-light applications, respectively.
Example
An optical remote or qualified optical assembly.
Important distinction
They are distinct devices; laser systems require their specified optical precautions.
Specifications to read
Forward/reverse voltage behavior, current, dissipation, recovery or response and application-specific limits.
A rating is a limit or condition, not a guarantee of suitability. Use the manufacturer's data sheet for the exact component and the equipment's schematic for its intended role.
LEDDiodes
What it does
Emits light when operated with an appropriate forward current and thermal design.
Example
A status indicator or illumination assembly.
Important distinction
An LED requires a suitable current-control circuit; color alone does not determine its limits.
Specifications to read
Forward/reverse voltage behavior, current, dissipation, recovery or response and application-specific limits.
A rating is a limit or condition, not a guarantee of suitability. Use the manufacturer's data sheet for the exact component and the equipment's schematic for its intended role.
PhotodiodeDiodes
What it does
Converts incident light into an electrical response used by a sensing circuit.
Example
An optical receiver or light meter.
Important distinction
Its operating bias and signal conditioning depend on the application.
Specifications to read
Forward/reverse voltage behavior, current, dissipation, recovery or response and application-specific limits.
A rating is a limit or condition, not a guarantee of suitability. Use the manufacturer's data sheet for the exact component and the equipment's schematic for its intended role.
Rectifier diodeDiodes
What it does
Conducts preferentially in one direction within its specified behavior, allowing rectification or directional current paths.
Example
Converting alternating input into unidirectional pulses.
Important distinction
Forward current, reverse voltage and recovery behavior must suit the circuit.
Specifications to read
Forward/reverse voltage behavior, current, dissipation, recovery or response and application-specific limits.
A rating is a limit or condition, not a guarantee of suitability. Use the manufacturer's data sheet for the exact component and the equipment's schematic for its intended role.
Schottky diodeDiodes
What it does
Uses a metal-semiconductor junction and has characteristics that can suit selected low-loss or fast applications.
Example
A converter or signal clamp.
Important distinction
Compare leakage, voltage and thermal requirements, not just forward drop.
Specifications to read
Forward/reverse voltage behavior, current, dissipation, recovery or response and application-specific limits.
A rating is a limit or condition, not a guarantee of suitability. Use the manufacturer's data sheet for the exact component and the equipment's schematic for its intended role.
TVS diodeDiodes
What it does
Designed to suppress specified transient events by limiting voltage during those events.
Example
An interface protection network.
Important distinction
It is not a substitute for a steady-state voltage regulator.
Specifications to read
Forward/reverse voltage behavior, current, dissipation, recovery or response and application-specific limits.
A rating is a limit or condition, not a guarantee of suitability. Use the manufacturer's data sheet for the exact component and the equipment's schematic for its intended role.
Varactor and PIN diodeDiodes
What it does
A varactor provides voltage-dependent junction capacitance. A PIN diode has a structure useful in selected RF or detection applications.
Example
Electronic tuning or RF switching.
Important distinction
These are distinct devices with application-specific behavior.
Specifications to read
Forward/reverse voltage behavior, current, dissipation, recovery or response and application-specific limits.
A rating is a limit or condition, not a guarantee of suitability. Use the manufacturer's data sheet for the exact component and the equipment's schematic for its intended role.
Zener diodeDiodes
What it does
Operates in a specified reverse-breakdown region for reference or limiting applications.
Example
A suitably designed voltage reference.
Important distinction
It needs a compatible current-limiting and power-dissipation arrangement.
Specifications to read
Forward/reverse voltage behavior, current, dissipation, recovery or response and application-specific limits.
A rating is a limit or condition, not a guarantee of suitability. Use the manufacturer's data sheet for the exact component and the equipment's schematic for its intended role.
Visual comparison guides
Compare representative physical forms, then read the entries for their different functions. Many parts share package shapes. Appearance alone cannot identify ratings, internal construction or terminal assignments.
Units and worked examples
| Quantity | Unit | Meaning |
|---|---|---|
| Voltage | V, volts | Potential difference between two points. |
| Current | A, amperes | Rate of charge flow. |
| Resistance | Ω, ohms | Resistance to current flow. |
| Power | W, watts | Rate of energy transfer or dissipation. |
| Capacitance | F, farads | Charge change per voltage change. |
| Inductance | H, henries | Relationship between current change and induced voltage. |
| Frequency | Hz, hertz | Cycles per second. |
Prefixes: k = 1,000; M = 1,000,000; m = 0.001; μ = 0.000001; n = 0.000000001; p = 0.000000000001. Case matters: M and m are different.
Resistor example
For an ideal 1 kΩ resistor with 5 V across it: I = V/R = 5/1,000 = 0.005 A = 5 mA. Dissipation is P = V²/R = 25/1,000 = 0.025 W. This arithmetic does not select a real part without its temperature, voltage and application requirements.
Tolerance example
A 1 kΩ resistor with ±5% nominal tolerance spans 950 Ω to 1,050 Ω at the specified conditions. Tolerance is different from drift with temperature or aging.
Capacitance and timing example
10 μF = 10,000 nF. An ideal first-order RC network with R = 1 kΩ and C = 10 μF has τ = RC = 0.01 s = 10 ms. A time constant is not automatically the delay of every timer using those parts.
Stored energy
Ideal capacitor charge is Q = CV; stored energy is E = ½CV². Doubling voltage at the same capacitance quadruples the stored energy. These are learning equations, not a discharge procedure.
Schematic symbols, labels and markings
Reference letters identify components in a drawing; conventions vary by manufacturer and standard. Always read the drawing's legend.
| Common label | Often used for |
|---|---|
| R | Resistor |
| C | Capacitor |
| L | Inductor |
| D | Diode |
| Q | Transistor |
| U / IC | Integrated circuit |
| T | Transformer |
| K / RL | Relay |
| SW / S | Switch |
| J / P / CN | Connector |
| F | Fuse |
| Y / X | Crystal or resonator |
| TP | Test point |
| V / VT | Tube in some historical documentation |
R17 identifies a component location, not a resistance value. A marking such as 4R7 may mean 4.7 Ω in an applicable resistor convention. Three-digit markings such as 104 often represent 100,000 base units: 100 kΩ for a resistor or 100,000 pF = 100 nF for an applicable capacitor code. Confirm the component family and marking system; short codes can be ambiguous.
Common questions
Can I replace a part with any higher-rated one?
No. A higher headline rating does not ensure suitable function, polarity, frequency behavior, package, protective approval or circuit stability.
Does a part that looks normal have to be good?
No. Visual observations can help, but many electrical changes leave no obvious external sign.
Are capacitance, ESR and leakage the same?
No. They describe different properties. A single test cannot establish every capacitor failure mode.
Can I measure every component while it remains connected?
Other paths can affect an in-circuit result. Interpretation depends on the circuit and instrument. Internal work also requires a suitable qualified safety procedure.
Does a matching package establish a transistor or IC replacement?
No. Pinout, function, voltage, drive, timing, heat and application requirements must match.
Is a component the same thing as a circuit?
A component is a building block. A circuit connects building blocks to perform a function. The same component family can serve many circuit roles.
How do I begin learning?
Start with units, schematic labels, resistor/capacitor/inductor functions and signal-versus-power paths. Use disconnected parts or an instructor-approved low-voltage trainer before considering customer equipment.
Is this reference free?
Yes. Every entry, example and reference on this page is public. The separate repair masterclasses have their own free previews and paid lessons.
Manufacturer references
Original plain-language summaries and educational examples. These references support further study; exact product data sheets and equipment manuals remain authoritative for a real application.
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