““RESISTORS”RESISTORS”

DEFINITIONDEFINITION

- It is an electronic component that has - It is an electronic component that has the ability to resist and/or oppose the the ability to resist and/or oppose the flow of free electrons (current).flow of free electrons (current).

Resistors RangeResistors Range

ValueValue

- From less than 1- From less than 1ΩΩ up to 20M up to 20MΩΩ

SizeSize

- Vary from microscopic up to - Vary from microscopic up to too large to carrytoo large to carry

Two categories:Two categories:1. Fixed resistors 1. Fixed resistors

2. Variable resistors2. Variable resistors

Fixed ResistorsFixed Resistors Have single value of resistance Have single value of resistance

Three Characteristics:Three Characteristics:1.1. ValueValue

2.2. Power ratingPower rating

3.3. ToleranceTolerance

VALUEVALUEIndicates the nominal or ideal amount Indicates the nominal or ideal amount

of resistanceof resistance

POWER RATINGPOWER RATING This indicates the This indicates the amount of power that amount of power that

can be dissipated for an can be dissipated for an indefinite amount of indefinite amount of

time without degrading time without degrading the performance of the the performance of the

resistorresistor Depends on the physical Depends on the physical

size of the resistorsize of the resistor

RESISTOR TOLERANCERESISTOR TOLERANCE

The allowable variation which The allowable variation which is expressed as a percentis expressed as a percent

Common resistor tolerance:Common resistor tolerance:

1%, 2%, 5%, 10%, & 20%1%, 2%, 5%, 10%, & 20%

Four major classes:Four major classes:

1. Carbon Composition1. Carbon Composition

2. Film 2. Film

3. Wirewound 3. Wirewound

4. Surface-Mount Technology (SMT)4. Surface-Mount Technology (SMT)

CARBON COMPOSITION CARBON COMPOSITION RESISTORRESISTOR

Use a mixture of carbon Use a mixture of carbon and an insulating filler and an insulating filler

as the resistive as the resistive element; this mixture element; this mixture

is pressed into a is pressed into a cylindrical form and cylindrical form and

coated with hard coated with hard nonconductive nonconductive

material.material.

FILM RESISTORSFILM RESISTORSMade by depositing a thin layer of Made by depositing a thin layer of resistive material onto an insulating resistive material onto an insulating

tube or rod called thetube or rod called the substrate. substrate.Use high-speed industrial laser for Use high-speed industrial laser for

trimming, as for the laser etches trimming, as for the laser etches away portions of the deposited film, away portions of the deposited film,

the higher the resistance is known as the higher the resistance is known as the process known as spiraling.the process known as spiraling.

DIFFERENT TYPES OF MATERIALS DIFFERENT TYPES OF MATERIALS USED FOR FILM RESISTOR:USED FOR FILM RESISTOR:

1.1. Carbon (Carbon Film)Carbon (Carbon Film)

2.2. Nickel – Chromium (Metal Film)Nickel – Chromium (Metal Film)

3.3. Metal & Glass (Metal Glaze Film)Metal & Glass (Metal Glaze Film)

4.4. Metal & Oxide Mixture (Metal Oxide)Metal & Oxide Mixture (Metal Oxide)

WIREWOUND RESISTORSWIREWOUND RESISTORS

- Are made by winding resistive wire Are made by winding resistive wire around an insulating rod.around an insulating rod.

Value of a particular wirewound Value of a particular wirewound resistor can be determined by the ff.:resistor can be determined by the ff.:

1.1. Type of wireType of wire

2.2. Diameter of the wireDiameter of the wire

3.3. Length of the wire used to wind the Length of the wire used to wind the resistorresistor

Appearance of Appearance of wirewound resistorswirewound resistors

Construction of wirewound resistorConstruction of wirewound resistor

SURFACE – MOUNT SURFACE – MOUNT RESISTORRESISTOR

- Have no leads, their contacts solder - Have no leads, their contacts solder directly to pads on the printed circuit directly to pads on the printed circuit board (PCB). It is commonly used board (PCB). It is commonly used when small size is an important when small size is an important consideration.consideration.

RESISTOR COLOR CODERESISTOR COLOR CODE

VARIABLE VARIABLE RESISTORSRESISTORS

The resistance of a variable The resistance of a variable resistor can be adjusted by resistor can be adjusted by turning a knob or a rotating turning a knob or a rotating

screw.screw.

2 Major types:2 Major types:1. Rheostat1. Rheostat

- Is a two (2) terminal device whose - Is a two (2) terminal device whose resistance can be change.resistance can be change.

2. Potentiometer2. Potentiometer

- Is a three (3) terminal device that is - Is a three (3) terminal device that is constructed much like a rheostat.constructed much like a rheostat.