The final band indicates the tolerance of the resistor. The third band is a weight value, which multiplies the two significant digits by a power of ten. In the standard four band resistors, the first two bands indicate the two most-significant digits of the resistor's value. Resistors in these arrays may share a common pin, or be set up as voltage dividers. Resistors may come in pre-wired packs of five-or-so resistor arrays. There are a variety of other, special-purpose resistors out there. In both resistor types, a small film of resistive metal alloy is sandwiched between a ceramic base and glass/epoxy coating, and then connected to the terminating conductive edges. Thick-film is usually cheaper but less precise than thin. Surface-mount resistors are usually either thick or thin-film variety. These resistors are usually more expensive, higher-end components specifically chosen for their unique characteristics like a higher power-rating, or maximum temperature range. Other through-hole resistors might be wirewound or made of super-thin metallic foil.
Inside the resistor, a carbon film is wrapped around an insulator. Resistance values from top to bottom: 27Ω, 330Ω and a 3.3MΩ. Peek inside the guts of a few carbon-film resistors. A common ½W resistor measures about 9.2mm across, while a smaller ¼W resistor is about 6.3mm long. The size of an axial resistor is relative to its power rating. The most common through-hole resistors come in an axial package. The long leads usually require trimming, and these resistors are bound to take up much more space than their surface-mount counterparts. These resistors are usually more useful in breadboarding, prototyping, or in any case where you'd rather not solder tiny, little 0.6mm-long SMD resistors. Through-hole resistors come with long, pliable leads which can be stuck into a breadboard or hand-soldered into a prototyping board or printed circuit board (PCB). These types of resistors are usually abbreviated as either PTH (plated through-hole) or SMD/SMT (surface-mount technology or device). Resistors will come in one of two termination-types: through-hole or surface-mount. They might be a standard, static resistor, a pack of resistors, or a special variable resistor. They might be through-hole or surface-mount. Resistors come in a variety of shapes and sizes. When modeled on a schematic, a resistor will show up as one of these two symbols: Schematic symbolĪll resistors have two terminals, one connection on each end of the resistor. For example, a 4,700Ω resistor is equivalent to a 4.7kΩ resistor, and a 5,600,000Ω resistor can be written as 5,600kΩ or (more commonly as) 5.6MΩ. It's very common to see resistors in the kilohm (kΩ) and megaohm (MΩ) range (much less common to see miliohm (mΩ) resistors). The (somewhat roundabout) definition of 1Ω is the resistance between two points where 1 volt (1V) of applied potential energy will push 1 ampere (1A) of current.Īs SI units go, larger or smaller values of ohms can be matched with a prefix like kilo-, mega-, or giga-, to make large values easier to read. The symbol for an ohm is the greek capital-omega: Ω. The electrical resistance of a resistor is measured in ohms. Commonly resistors are used to limit current, divide voltages, and pull-up I/O lines. Resistors are usually added to circuits where they complement active components like op-amps, microcontrollers, and other integrated circuits. They are passive components, meaning they only consume power (and can't generate it). The resistor's resistance limits the flow of electrons through a circuit. Resistors are electronic components which have a specific, never-changing electrical resistance.