Basic Electronic Elements

Resistor• Two-terminal electronic component that opposes the

flow of current through it an drops a voltage across its terminals that is proportional to the electric current through it in accordance with Ohm's law:

V=IR• It’s a Passive Component• Primary characteristics of a resistor are

– Resistance– Tolerance (Accuracy of R)– Maximum voltage– Power rating– Temperature coefficient.

Resistor• Units & Symbol

– The ohm (symbol: Ω) is the SI unit of electrical resistance– milliohm (1x10−3), kilo ohm (1x103), and mega ohm (1x106)

• Power dissipation

– If the average power dissipated is more than the resistor can safely dissipate, the resistor may depart from its normal resistance value.

– Excessive power dissipation may raise the temperature of the resistor to a point where it burns out.

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Color Coding• axial resistors uses colored stripes.• Surface-mount resistors are marked numerically.• Resistor values are always coded in ohms.

– band A is first significant figure of component value– band B is the second significant figure– band C is the decimal multiplier– band D if present, indicates tolerance of value

in percent (no color means 20%)

The measurement unit "ppm" is parts per million or 10,000 times smaller than the unit "%”

Resistor (AXIAL)

• Temperature CoefficientThe "alpha" (α) constant is known as the temperature coefficient of resistance, and symbolizes the resistance change factor per degree of temperature change.

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ResistorExample

yellow, violet, red, and gold – First digit yellow = 4– second digit violet = 7 – followed by 2 (red) zeros or 102

– Answer: 4,700 ohms– Gold signifies that the tolerance is ±5%, so the real

resistance could lie anywhere between 4,465 and 4,935 ohms.

(5% of 4700Ω = 235Ω)

4700 + 235 = 495 Ω & 4700 – 235 = 4465Ω

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Question?What is the Resistor Value and its tolerance?

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Answer:

Brown = 1Black= 0Yellow= 4R= 10 x 10000 = 100K ohm

Tolerance: Gold 5% through-hole resistor

BBRoyGreatBritianVeryGoodWifeGoesSwimming

• 5-band axial resistors• 5-band identification is used for higher precision (lower

tolerance) resistors (1 percent, 0.5 percent, 0.25 percent, 0.1 percent), to notate the extra digit.

• The first three bands represent the significant digits, the fourth is the multiplier, and the fifth is the tolerance.

• Five-band standard tolerance resistors are sometimes encountered, generally on older or specialized resistors. They can be identified by noting a standard tolerance color in the fourth band. The fifth band in this case is the temperature coefficient.

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ResistorSurface Mount Packages

SMD resistors use alphanumeric codes, not colors

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• Method 1– manufacturer prints 3 digits on components:

2 value digits followed by the power of ten multiplier– resistor marked 472 is 4,700 Ω

• Method 2– a 4-digit code which has 3 significant figures and a power of ten

multiplier– 4701 would represent a 4700 Ω = 4.70 KΩ

• Method 3– Another way is to use the "kilo-" or "mega-" prefixes in place of

the decimal point:– 1K2 = 1.2 kΩ = 1,200 Ω – M47 = 0.47 MΩ = 470,000 Ω – 68R = 68 Ω

SMD resistors values reading methods

Method- 1 (3 Digit Code)

• "334" = 33 × 10,000 ohms = 330 kilohms • "222" = 22 × 100 ohms = 2.2 kilohms • "473" = 47 × 1,000 ohms = 47 kilohms • "105" = 10 × 100,000 ohms = 1 megohm Resistances less than 100 ohms are written: 100, 220, 470. The final zero represents ten to the power zero, which is 1. For example:• "100" = 10 × 1 ohm = 10 ohms • "220" = 22 × 1 ohm = 22 ohms • “470" = 47 × 1 ohm = 47 ohms

Sometimes these values are marked as "10" or "22" to prevent a mistake.

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Method- 2 (4 Digit Code)Precision resistors are marked with a four-digit code, in which the first three digits are the significant figures and the fourth is the power of ten.

For example:• "1001" = 100 × 10 ohms = 1 kilohm • "4992" = 499 × 100 ohms = 49.9 kilohm • "1000" = 100 × 1 ohm = 100 ohms "000" and • "0000" sometimes appear as values on surface-mount zero-ohm

links, since these have (approximately) zero resistance.

Resistances less than 10 ohms have 'R' to indicate the position of the decimal point (radix point).

For example:• "4R7" = 4.7 ohms "0R22" = 0.22 ohms • "0R01" = 0.01 ohms

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For SMT Resistors

ResistorIndustrial type designation

Format: [two letters]<space>[resistance value (three digit)] <nospace> [ tolerance

code(numerical - one digit)]

• The operational temperature range distinguishes commercial grade, industrial grade and military grade components.

• Commercial grade: 0 °C to 70 °C• Industrial grade: −40 °C to 85 °C (sometimes −25 °C to 85 °C)• Military grade: −55 °C to 125 °C (sometimes -65 °C to 275 °C)• Standard Grade -5°C to 60°C

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SIL Resistor packageA single in line (SIL) resistor package with 8 individual, 47 ohm resistors. One end of each resistor is connected to a separate pin and the other ends are all connected together to the remaining (common) pin - pin 1, at the end identified by the white dot.

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Variable ResistorPotentiometer, informally, a POT, is a three-terminal resistor with a sliding contact that forms an adjustable voltage divider. If only two terminals are used (one side and the wiper), it acts as a variable resistor or Rheostat.

Potentiometers are commonly used to control electrical devices such as volume controls on audio equipment

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PCB variable resistors

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Trimmer Potentiometer

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Faders (volume type)

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