Resistor

Resistor is an electrical component that reduces the electrical current.

The resistor has resistance that is measured in units of Ohms [Ω].

If we make an analogy to water flow in pipes, the resistor is a thin pipe that reduces the water flow.

Resistor picture

Resistor symbols

IEEE symbol (US)
IEC symbol (Europe)

Resistor color code

The resistance of the resistor and its tolerance are marked on the resistor with color code bands that denotes the resistance value.

There are 3 types of color codes:

• 4 bands: digit, digit , multiplier, tolerance.
• 5 bands: digit, digit, digit , multiplier, tolerance.
• 6 bands: digit, digit, digit , multiplier, tolerance, temperature coefficient.

Color codes table

		1st Digit		2nd Digit		3rd Digit		Multiplier		Tolerance		Temperature Coefficient
4bands		1		2				3		4
5bands		1		2		3		4		5
6bands		1		2		3		4		5		6
Black		0		0		0		×100
Brown		1		1		1		×101		±1%		100 ppm/ºK
Red		2		2		2		×102		±2%		50 ppm/ºK
Orange		3		3		3		×103				15 ppm/ºK
Yellow		4		4		4		×104				25 ppm/ºK
Green		5		5		5		×105		±0.5%
Blue		6		6		6		×106		±0.25%		10 ppm/ºK
Violet		7		7		7		×107		±0.1%		5 ppm/ºK
Grey		8		8		8		×108		±0.05%
White		9		9		9		×109
Silver								×10-2		±10%
Gold								×10-1		±5%
None										±20%

Resistance calculation of 4 bands resistor

R = (10×digit₁+digit₂)×multiplier

Resistance calculation of 5 or 6 bands resistor

R = (100×digit₁+10×digit₂+digit₃)×multiplier

Resistor types

Variable resistor	Variable resistor has an adjustable resistance (2 terminals)
Potentiometer	Potentiometer has an adjustable resistance (3 terminals)
Photo-resistor	Reduces resistance when exposed to light
Power resistor	Power resistor is used for high power circuits and has large dimensions.
Surface mount (SMT/SMD) resistor	SMT/SMD resistors have small dimensions. The resistors are surface mounted on the printed circuit board (PCB), this method is fast and requires small board area.
Resistor network	Resistor network is a chip that contains several resistors with similar or different values.
Carbon resistor
Chip resistor
Metal-oxide resistor
Ceramic resistor

 

Pull-up resistor

In digital circuits, pull-up resistor is a regular resistor that is connected to the high voltage supply (e.g +5V or +12V) and sets the input or output level of a device to '1'.

The pull-up resistor set the level to '1' when the input / output is disconnected. When the input / output is connected, the level is determined by the device and overrides the pull-up resistor.

Pull-down resistor

In digital circuits, pull-down resistor is a regular resistor that is connected to the ground (0V) and sets the input or output level of a device to ' 0 '.

The pull-down resistor set the level to ' 0 ' when the input / output is disconnected. When the input / output is connected, the level is determined by the device and overrides the pull-down resistor.

Resistors types

 

 

Electrical resistance ►

 

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See also

• Electrical resistance
• Resistor symbols
• Ohm
• Ohm's law
• Capacitor
• Inductor
• Resistor - Wikipedia
• Resistors Manufacturer - Vishay