One of the most common electronic components is the resistor. As the name implies, these devices resist the flow of electric current. Resistors play a very important role in electrical circuits—not because they simply resist current, but because they resist it in a precise and controllable way.
The unit that we use to specify the resistance of a resistor is the ohm, denoted by the symbol Ω. A resistor with very low resistance—for example, less than 1 Ω—could be considered a conductor. If the resistance is in the tens of millions of ohms, the resistor will function like an insulator. Moderate values of resistance, such as 470 Ω or 10,000 Ω, don’t really fit into the conductor category or the insulator category.
Much types of Resistors, is the most commonly used of all electronic components. There are different types of resistors are available with their primary function is to limit the current through the electrical circuit and to lower the voltage. Resistors are "Passive Components", which does not contain a source of strength / reinforcement, but only weaken or reduce the signal voltage there are past them. When used in circuits generated DC Drop Voltage terminal was measured in both legs. Resistor produces a voltage drop when an electric current flowing through it in accordance with Ohm's Law, with different values on each of resistor produces different values of currents or voltages.
This is very useful in electronic circuitry to control or reduce both current and voltage generated after flowing through it. There are different type of resistors and manufactured in various forms because of certain characteristics and accuracy in accordance with the specific application fields, such as the High Stability, High Voltage, High Current, etc., or used as general purpose resistors where their characteristics are less of a problem. Some common characteristics associated with low resistor such as; Temperature Coefficient, Coefficient Voltage, Noise, Frequency Response, Power and Temperature Rating, Physical Size and Reliability.
Resistor Band Colors / reading resistor color code values
As shown left, a carbon-composition resistor can have 4 to 6 bands. A 5-band resistor is more precise compared to a 4-band type because of the inclusion of a third significant digit. A 6-band resistor is like a 5-band resistor but includes a temperature coefficient band (the 6th band).
| 4-band | 5-band | 6-band | |
|---|---|---|---|
| 1st band | 1st significant digit | 1st significant digit | 1st significant digit |
| 2nd band | 2nd significant digit | 2nd significant digit | 2nd significant digit |
| 3rd band | multiplier | 3rd significant digit |
3rd significant digit |
| 4th band | tolerance | multiplier | multiplier |
| 5th band | N/A | tolerance | tolerance |
| 6th band | N/A | N/A | temperature coefficient |
Each color represents a number if it's located from the 1st to 2nd band for a 4-band type or 1st to 3rd band for a 5-band and 6-band type.
| Color | Value |
|---|---|
|
Black (2nd and 3rd bands only) |
0 |
| Brown | 1 |
| Red | 2 |
| Orange | 3 |
| Yellow | 4 |
| Green | 5 |
| Blue | 6 |
| Violet | 7 |
| Grey | 8 |
| White | 9 |
Mnemonics were created to easily memorize the sequence of the colors. The most popular mnemonic is "Big Boys Race Our Young Girls But Violet Generally Wins" where the first letter of each word corresponds to the first letter of the color.
If the color is found on the 3rd band for a 4-band type or the 4th band for a 5-band and 6-band type, then it's a multiplier.
| Color | Value |
|---|---|
|
Black |
x1 |
| Brown | x10 |
| Red | x100 |
| Orange | x1000 |
| Yellow | x10000 |
| Green | x100000 |
| Blue | x1000000 |
| Violet | x10000000 |
| Grey | x100000000 |
| White | x1000000000 |
Notice that the number of zeroes is equal to the color's number as per the previous table.
The fourth band (or 5th for the 5-band and 6-band) indicates the tolerance values. Here, two colors are added (gold and silver).
| Color | Value |
|---|---|
|
Black |
N/A |
| Brown | ±1% |
| Red | ±2% |
| Orange | ±3% |
| Yellow | ±4% |
| Green | ±0.5% |
| Blue | ±0.25% |
| Violet | ±0.10% |
| Grey | ±0.05% |
| White | N/A |
| Gold | ±5% |
| Silver | ±10% |
The 6th band for a 6-band type resistor is the temperature coefficient. This indicates how much the actual resistance value of the resistor changes when the temperature changes.
| Color | Value |
|---|---|
|
Black |
N/A |
| Brown | 100 ppm/ºC |
| Red | 50 ppm/ºC |
| Orange | 15 ppm/ºC |
| Yellow | 25 ppm/ºC |
| Green | N/A |
| Blue | 10 ppm/ºC |
| Violet | 5 ppm/ºC |
| Grey | N/A |
| White | N/A |
Color Code Exceptions
5 Band Resistor with a 4th Band of Gold or Silver
Five band resistors with a fourth band of silver or gold form an exception, and are utilized on specific or older resistors. The first two bands represent the significant digits, the third band is a multiplication factor, the fourth band is for tolerance and the fifth band is for the temperature coefficient (ppm/K).
Deviating Colors
In order to prevent metal and other particles from getting in the coating of high voltage resistors, the gold and silver bands are often replaced with a yellow and gray band.
Single Black Band or Zero-Ohm Resistor
A single black band on a resistor is called a zero-ohm resistor. Basically, it is a wire link used to connect traces on a printed circuit board (PCB) that is packaged in the same physical package format as a resistor. This packaging allows the zero-ohm resistor to be placed on the circuit board using the same equipment typically used to place other resistors.
Reliability Band
When resistors are produced in accordance to military specifications, they will often include a band that indicates reliability. This band is specifically for failure rate percentage per 1000 hours of service. This band is almost never used in commercial electronics. Four band resistors typically use this reliability band. For more information about this can be found in the US military handbook MIL-HDBK-199.
Resistor Materials
Resistors can be found in a variety of different materials, each one with its own properties and specific areas of use. Most electrical engineers use the types found below:
Wirewound (WW) Resistors
Wire Wound Resistors are manufactured by winding resistance wire around a non-conductive core in a spiral. They are typically produced for high precision and power applications. The core is usually made of ceramic or fiberglass and the resistance wire is made of nickel-chromium alloy and are not suitable for applications with frequencies higher than 50kHz.
Low noise and stability with respect to temperature variations are standard characteristics of Wire Wound Resistors. Resistance values are available from 0.1 up to 100 kW, with accuracies between 0.1% and 20%.
With a metallic body as a heat absorbers, have a very high value of watts
Other types of resistors, wire wound resistors are called, are made by winding a thin wire metal alloy (Nichrome) or wire type of to ceramic insulators in the form of a spiral helix that is similar to Film Resistors. Resistors of this type are generally only available Ohm very low with high precision (from 0.01 to 100kΩ). These resistors are widely used in the instrument gauges on a Whetstone bridge circuit. This resistor also able to handle the electrical current is much higher than others with Ohm resistor the same value with a power rating of more than 300 Watts. Resistors of this type are called "Chassis Mounted Resistors". They are designed to be physically mounted on a heatsink or metal plate to further remove the heat generated thereby enhancing the ability of a current greater.
Wire wound resistor of this type begins with the notation "WH" or "W" (for example; WH10Ω) and are available in packs Aluminum Cladded (WH) with accuracy (± 1%, ± 2%, ± 5% & ± 10% tolerance) or the vitreous Enamelled W package (± 1%, ± 2% & ± 5% tolerance) with 1W power up to 300W or more
Metal Film Resistors
Nichrome or tantalum nitride is typically used for metal film resistors. A combination of a ceramic material and a metal typically make up the resistive material. The resistance value is changed by cutting a spiral pattern in the film, much like carbon film with a laser or abrasive. Metal film resistors are usually less stable over temperature than wire wound resistors but handle higher frequencies better.
Metal Film Resistors or cermets resistors - Made of conductive metal oxide paste, for very low power
"Film Resistors" consists of Metal Film, Carbon Film and Metal Oxide Films, which is typically made by depositing a pure metal coating, such as nickel, or oxide films, such as tin-oxide, the ceramic insulator rods or substrate. Resistive value of resistor is lowered by the thickness of the film were then given a helical groove by using laser light. This raises the effect of increasing the resistance because the conductive layer or a helical cut in the same result by wrapping the wire in coil form. This manufacturing method allows for the resistors of this type has a higher accuracy than the Carbon Resistor.
Metal Film Resistors have a much better temperature stability than carbon resistors are equal in size the level of noise / low noise and generally better for high frequency or radio frequency applications. Metal Oxide Resistors better capability in high waves with a much higher temperature capability than equivalent metal film resistors. Other types of film resistors is commonly known as the Thick Film Resistors made by superimposing a thicker conductive paste of ceramic and metal, called cermet, the alumina ceramic substrate. Such resistors are used in the manufacture of small electronic circuits such as in the manufacture of PCBs for Calculator, mobile phones and computer peripherals devices la. Has a temperature stability, low noise, and the proper voltage. Metal Film Resistors begins with the notation "MFR" (eg MFR100kΩ) and CF for Carbon Film types. Metal film resistors are available in the trajectory E24 (± 5% & ± 2% tolerance), E96 (± 1% tolerance) and E192 (± 0.5%, ± 0.25% & ± 0.1% tolerance) with the power of 0, 05 (1 / 20) Watt up to 1 / 2 Watt. In general, precision film resistors are low power components.
Metal Oxide Film Resistors
Metal oxide resistors use metal oxides such as tin oxide, making them slightly different from metal film resistors. These resistors are reliable and stable and operate at higher temperatures than metal film resistors. Because of this, metal oxide film resistors are used in applications that require high endurance.
Foil Resistors
Developed in the 1960s, the foil resistor is still one of the most accurate and stable types of resistor that you’ll find and are used for applications with high precision requirements. A ceramic substrate that has a thin bulk metal foil cemented to it makes up the resistive element. Foil Resistors feature a very low-temperature coefficient of resistance.
Carbon Composition (CCR) Resistors
Until the 1960s Carbon Composition Resistors were the standard for most applications. They are reliable, but not very accurate (their tolerance cannot be better than about 5%). A mixture of fine carbon particles and non-conductive ceramic material are used for the resistive element of CCR Resistors.
The substance is molded into the shape of a cylinder and baked. The dimensions of the body and the ratio of carbon to ceramic material determine the resistance value. More carbon used in the process means there will be a lower resistance. CCR resistors are still useful for certain applications because of their ability to withstand high energy pulses, a good example application would be in a power supply.
Carbon Resistors is the Composite Resistors that most common for use in the use of any electronic circuit common and is considered the most expensive resistors. It's resistive element is made from a mixture of carbon powder or carbon graphite (like pencil leads) with ceramic (clay). The ratio of carbon to determine the overall value of resistive ceramic mixture and the higher this ratio the lower the resistance value. The mixture is then formed into a cylindrical shape and metal wire / conductor attached to each end, to provide electrical connections before the outside is coated with insulating material and color-coded signs.
Carbon Composite Resistors have a low to medium power with a low inductance which makes it ideal for high frequency applications, but has a weakness at the level of noise (high noise) and less stable in hot conditions. Identification of carbon composite resistors are prefixed with "CR" (eg CR10kΩ) and is available in Path E6 (± 20% tolerance), Panorama of E12 (± 10% tolerance) and the Panorama of E24 (± 5% & ± 2% tolerance) resistor type generally it has a power of 0.125 or 1 / 4 Watt to 2 Watt.
Carbon Film Resistors
Carbon film resistors have a thin carbon film (with a spiral cut in the film to increase the resistive path) on an insulating cylindrical core. This allows for the resistance value to be more accurate and also increases the resistance value. Carbon film resistors are much more accurate than carbon composition resistors. Special carbon film resistors are used in applications that require high pulse stability.
Key Performance Indicators (KPIs)
The KPIs for each resistor material can be found below:
| Characteristic | Metal Film | Thick Metal Film | Precision Metal Film | Carbon Composition | Carbon Film |
|---|---|---|---|---|---|
| Temp. range | -55+125 | -55+130 | -55+155 | -40+105 | .55+155 |
| Max. temp. coeff. | 100 | 100 | 15 | 1200 | 250-1000 |
| Vmax | 200-350 | 250 | 200 | 350-500 | 350-500 |
| Noise (μV per volt of applied DC) | 0.5 | 0.1 | 0.1 | 4 (100K) | 5 (100K) |
| R Insul. | 10000 | 10000 | 10000 | 10000 | 10000 |
| Solder (change % in resistance value) | 0.20% | 0.15% | 0.02% | 2% | 0.50% |
| Damp heat (change % in resistance value) | 0.50% | 1% | 0.50% | 15% | 3.50% |
| Shelf life (change % in resistance value) | 0.10% | 0.10% | 0.00% | 5% | 2% |
| Full rating (2000h at 70degC) | 1% | 1% | 0.03% | 10% | 4% |
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