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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Aluminum electrolytic capacitorCapacitors
What it does
Provides relatively large capacitance in a compact package; many common versions are polarized.
Example
Bulk supply smoothing.
Important distinction
Polarity, ripple-current capability, ESR and temperature requirements matter.
Specifications to read
Capacitance (F), tolerance, voltage, polarity, dielectric, ESR, leakage, ripple capability and temperature 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.
Bipolar electrolytic capacitorCapacitors
What it does
Designed for applications without a fixed capacitor polarity within its specified limits.
Example
An appropriate audio network.
Important distinction
Bipolar does not mean suitable for arbitrary mains or pulse service.
Specifications to read
Capacitance (F), tolerance, voltage, polarity, dielectric, ESR, leakage, ripple capability and temperature 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.
C0G and NP0 ceramic dielectricCapacitors
What it does
Temperature-compensating ceramic classification commonly selected where capacitance stability matters.
Example
A suitable tuning or precision timing application.
Important distinction
Capacitance, voltage and specific series limits must still be checked.
Specifications to read
Capacitance (F), tolerance, voltage, polarity, dielectric, ESR, leakage, ripple capability and temperature 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.
Capacitor ESR and leakageCapacitors
What it does
ESR describes an equivalent resistive loss; leakage describes nonideal conduction through a capacitor's insulation.
Example
A capacitor assessment record.
Important distinction
One favorable measurement does not establish all operating properties.
Specifications to read
Capacitance (F), tolerance, voltage, polarity, dielectric, ESR, leakage, ripple capability and temperature 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.
Capacitor fundamentalsCapacitors
What it does
Stores energy in an electric field and responds to voltage change. Capacitance is measured in farads, commonly expressed as microfarads, nanofarads or picofarads.
Example
Timing, coupling, filtering and supply decoupling.
Important distinction
Stored charge can remain after power removal; voltage rating is not a discharge guarantee.
Specifications to read
Capacitance (F), tolerance, voltage, polarity, dielectric, ESR, leakage, ripple capability and temperature 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.
Capacitor ripple current and deratingCapacitors
What it does
Ripple capability concerns alternating current and heating; derating concerns operating margin relative to specified limits.
Example
A power-supply selection review.
Important distinction
Do not choose by capacitance and voltage alone.
Specifications to read
Capacitance (F), tolerance, voltage, polarity, dielectric, ESR, leakage, ripple capability and temperature 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.
Ceramic capacitorCapacitors
What it does
Uses ceramic dielectric. Different dielectric classes have different stability and operating behavior.
Example
High-frequency bypassing or a timing network.
Important distinction
Do not assume every ceramic retains its nominal capacitance under all conditions.
Specifications to read
Capacitance (F), tolerance, voltage, polarity, dielectric, ESR, leakage, ripple capability and temperature 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.
Film capacitorCapacitors
What it does
Uses a plastic-film dielectric, with different materials and electrode constructions available.
Example
Signal coupling or a specified pulse circuit.
Important distinction
Film type, pulse capability and ratings can matter as much as capacitance.
Specifications to read
Capacitance (F), tolerance, voltage, polarity, dielectric, ESR, leakage, ripple capability and temperature 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.
Mica and paper capacitorsCapacitors
What it does
Mica and historical paper dielectric parts are distinct technologies. Identification is important when studying old equipment.
Example
A tuned receiver circuit or historical coupling network.
Important distinction
Do not treat different dielectrics as one replacement family.
Specifications to read
Capacitance (F), tolerance, voltage, polarity, dielectric, ESR, leakage, ripple capability and temperature 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.
Polyester film capacitorCapacitors
What it does
A film construction used in many suitable general signal applications.
Example
An applicable coupling network.
Important distinction
Do not assume it matches every polypropylene or historical capacitor requirement.
Specifications to read
Capacitance (F), tolerance, voltage, polarity, dielectric, ESR, leakage, ripple capability and temperature 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.
Polymer capacitorCapacitors
What it does
Uses a conductive polymer system in applicable capacitor constructions. Often selected for low-impedance supply applications.
Example
A regulator's specified output network.
Important distinction
Low ESR is not automatically compatible with every regulator design.
Specifications to read
Capacitance (F), tolerance, voltage, polarity, dielectric, ESR, leakage, ripple capability and temperature 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.
Polypropylene film capacitorCapacitors
What it does
A film construction used in appropriate signal and pulse applications.
Example
A specified coupling or pulse network.
Important distinction
Pulse, AC and temperature suitability depend on the actual part.
Specifications to read
Capacitance (F), tolerance, voltage, polarity, dielectric, ESR, leakage, ripple capability and temperature 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.
Supercapacitor and safety capacitorCapacitors
What it does
A supercapacitor supports large charge storage in suitable low-voltage designs. Safety capacitors have specific interference-suppression approvals and application classes.
Example
Backup energy or approved line-interference suppression.
Important distinction
These are different families; a high voltage marking alone is not a safety approval.
Specifications to read
Capacitance (F), tolerance, voltage, polarity, dielectric, ESR, leakage, ripple capability and temperature 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.
Tantalum capacitorCapacitors
What it does
Uses tantalum-based construction, usually with a polarized form. Device technology and application limits vary.
Example
Compact supply storage on a circuit board.
Important distinction
Polarity and surge/application requirements are essential selection criteria.
Specifications to read
Capacitance (F), tolerance, voltage, polarity, dielectric, ESR, leakage, ripple capability and temperature 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.
Variable and trimmer capacitorCapacitors
What it does
Changes capacitance mechanically or by an adjustable structure, allowing tuning or calibration.
Example
An older radio tuning assembly.
Important distinction
Mechanical range and circuit function must match the design.
Specifications to read
Capacitance (F), tolerance, voltage, polarity, dielectric, ESR, leakage, ripple capability and temperature 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.
X-class safety capacitorCapacitors
What it does
An interference-suppression capacitor approved for its specified across-line application class.
Example
An approved mains interference network.
Important distinction
Use the required approvals and class; it is not a general-purpose capacitor substitution.
Specifications to read
Capacitance (F), tolerance, voltage, polarity, dielectric, ESR, leakage, ripple capability and temperature 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.
X7R and X5R ceramic dielectricCapacitors
What it does
Ceramic classifications describing specified temperature behavior; capacitance can also depend on operating bias.
Example
Compact supply decoupling.
Important distinction
The marked nominal value is not necessarily the effective value in the actual circuit.
Specifications to read
Capacitance (F), tolerance, voltage, polarity, dielectric, ESR, leakage, ripple capability and temperature 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.
Y-class safety capacitorCapacitors
What it does
An interference-suppression capacitor approved for specified applications involving an isolation or line-to-earth relationship.
Example
An approved interference path.
Important distinction
Required class, leakage and system safety must be preserved by qualified personnel.
Specifications to read
Capacitance (F), tolerance, voltage, polarity, dielectric, ESR, leakage, ripple capability and temperature 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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