Variant Of Resistor
Variant Of Resistor
Axial resistors have two leads that emerge from opposite ends of a usually cylindrical body. Radial resistors have parallel leads emerging from one side of the body and are unusual.
Precision resistors are generally defined as having a tolerance of no more than plus-or-minus 1%.
General-purpose resistors are less stable, and their value is less precise.
Power resistors are generally defined as dissipating 1 or 2 watts or more, particularly in power supplies or power amplifiers. They are physically larger and may require heat sinks or fan cooling.
Wire-wound resistors are used where the component must withstand substantial heat. A wirewound resistor often consists of an insulating tube or core that is flat or cylindrical, with multiwire is usually a nickel-chromium alloy known as nichrome (sometimes written as Ni-chrome) and is dipped in a protecting coating.
The heat created by current passing through resistive wire is a potential problem in electronic circuits where temperature must be limited. However, in household appliances such as hair dryers, toaster ovens, and fan heaters, a nichrome element is used specifically to generate heat. Wire-wound resistors are also used in 3D printers to melt plastic (or some other compound) that forms the solid output of the device.
Thick film resistors are sometimes manufactured in a flat, square format. A sample is shown in the following figure, rated to dissipate 10W from its flat surface. The resistance of this component is 1K.
Surface-mount resistors generally consist of a resistive ink film printed on top of a tablet of aluminum oxide ceramic compound, often approximately 6mm long, known as a 2512 form factor. Each surface-mount resistor has two nickelplated terminations coated in solder, which melts when the resistor is attached to the circuit board. The upper surface is coated, usually with black epoxy, to protect the resistive element.
This is also known as a resistor network or resistor ladder, and consists of a chip containing multiple equal-valued resistors.
A resistor array in a single-inline package (or SIP) may have three possible internal configurations: isolated, common bus, and dual terminator. These options are shown at top, center, and bottom, respectively, in the following figure. The isolated variant is commonly available in SIPs with 6, 8, or 10 pins. The common-bus and dual-terminator configurations generally have 8, 9, 10, or 11 pins.
In the isolated configuration, each resistor is electrically independent of the others and is accessed via its own pair of pins. On a common bus, one end of each resistor shares a bus accessed by a single pin, while the other ends of the resistors are accessed by their own separate pins. A dualterminator configuration is more complex, consisting of pairs of resistors connected between ground and an internal bus, with the midpoint of each resistor pair accessible via a separate pin. The resistor pairs this function as voltage dividers and are commonly used in emitter-coupled logic circuits that require termination with -2 volts.
A dual-inline package (DIP) allows a similar range of internal configurations, as shown in the following figure. At top, isolated resistors are commonly available in DIPs with 4, 7, 8, 9, or 10 pins. At center, the common bus configuration is available in DIPs with 8, 14, 16, 18, or 20 pins. At bottom, the dual-terminator configuration usually has 8, 14, 16, 18, or 20 pins.
The external appearance of SIP and DIP resistor arrays is shown in the following figure. From left to right, the packages contain seven 120Ω resistors in isolated configuration; thirteen 120Ω resistors in bussed configuration; seven 5.6K resistors in bussed configuration; and six 1K resistors in bussed configuration.
Resistor arrays with isolated or common-bus configurations are a convenient way to reduce the component count in circuits where pullup, pulldown, or terminating resistors are required for multiple chips. The common-bus configuration is also useful in conjunction with a 7-segment LED display, where each segment must be terminated by a series resistor and all the resistors share a common ground or common voltage source.
Surface-mount chips are available containing a pair of resistor configured as a single voltage divider.