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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10 of 160 entries shown. Search matches all entered words across names and explanations.
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Battery management and chargerPower Sources and Outputs
What it does
A system manages charging and relevant protection/monitoring for a specified cell arrangement.
Example
A rechargeable product.
Important distinction
Cell chemistry, series count and sensing arrangements must match the design.
Specifications to read
Source/load compatibility, polarity, current, chemistry where relevant, interface, mechanical and thermal conditions.
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.
BuzzerPower Sources and Outputs
What it does
Produces an audible indication using an internal or externally supplied drive arrangement.
Example
An alarm or status sound.
Important distinction
Active and passive buzzer types require different drive signals.
Specifications to read
Source/load compatibility, polarity, current, chemistry where relevant, interface, mechanical and thermal conditions.
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.
DC adapter and isolated supplyPower Sources and Outputs
What it does
Converts an available source into a specified output; some supplies provide certified isolation.
Example
A documented low-voltage trainer.
Important distinction
Output voltage, polarity, current and safety properties must be verified separately.
Specifications to read
Source/load compatibility, polarity, current, chemistry where relevant, interface, mechanical and thermal conditions.
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.
Heat sink and thermal interfacePower Sources and Outputs
What it does
Helps transfer dissipated heat from a component to its surroundings.
Example
A power amplifier or regulator.
Important distinction
Mounting, insulation and thermal resistance are part of the design, not cosmetic details.
Specifications to read
Source/load compatibility, polarity, current, chemistry where relevant, interface, mechanical and thermal conditions.
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.
LCD and OLED displayPower Sources and Outputs
What it does
LCD modulates light through a display arrangement; OLED emits light from its active display elements.
Example
A receiver interface or instrument.
Important distinction
Driver, interface, voltage and panel revision determine compatibility.
Specifications to read
Source/load compatibility, polarity, current, chemistry where relevant, interface, mechanical and thermal conditions.
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.
Motor and solenoidPower Sources and Outputs
What it does
A motor produces rotational or other sustained motion; a solenoid provides a magnetic actuator function.
Example
A cassette mechanism or controlled latch.
Important distinction
Stall current, inductive behavior and mechanical load affect the driver.
Specifications to read
Source/load compatibility, polarity, current, chemistry where relevant, interface, mechanical and thermal conditions.
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.
Primary battery and rechargeable cellPower Sources and Outputs
What it does
A primary cell is intended for non-rechargeable service; rechargeable chemistry requires its specified charging method.
Example
A portable device supply.
Important distinction
Do not apply one chemistry's charger to another or treat every cell as interchangeable.
Specifications to read
Source/load compatibility, polarity, current, chemistry where relevant, interface, mechanical and thermal conditions.
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.
Seven-segment displayPower Sources and Outputs
What it does
Groups visual segments into numeric or limited character indications.
Example
A counter or meter.
Important distinction
Common-anode/common-cathode and drive requirements differ.
Specifications to read
Source/load compatibility, polarity, current, chemistry where relevant, interface, mechanical and thermal conditions.
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.
SpeakerPower Sources and Outputs
What it does
Converts an electrical audio signal into sound through its transducer mechanism.
Example
An amplifier output load.
Important distinction
Impedance, power, enclosure and output topology influence suitability.
Specifications to read
Source/load compatibility, polarity, current, chemistry where relevant, interface, mechanical and thermal conditions.
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.
Stepper and servo systemPower Sources and Outputs
What it does
A stepper moves through driven phase sequences; a servo uses a feedback/control arrangement to achieve a commanded result.
Example
An instrument or positioning trainer.
Important distinction
A servo is a system concept, not simply a motor with a different connector.
Specifications to read
Source/load compatibility, polarity, current, chemistry where relevant, interface, mechanical and thermal conditions.
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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