Types Of Resistor.

                                                                          Types Of Resistor:

1. Thermistor.
2. Surface Mounted Device(SMD).
3. Wire Wound Resistor.
4. Film Type Resistor.
5. Carbon Type Resistor.
6. Fusible Resistor.


                                                                              1. Thermistor:

     A thermistor is a type of resistor whose resistance varies significantly with temperature, more so than in standard resistors. The word is a portmanteau of thermal and resistor. Thermistors are widely used as inrush current limiters, temperature sensors, self-resetting overcurrent protectors, and self-regulating heating elements.

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                                          2. Surface Mounted Device(SMD):

       Surface-mount technology (SMT) is a method for producing electronic circuits in which the components are mounted or placed directly onto the surface of printed circuit boards (PCBs). An electronic device so made is called a surface-mount device (SMD). In the industry it has largely replaced the through-hole technology construction method of fitting components with wire leads into holes in the circuit board. Both technologies can be used on the same board for components not suited to surface mounting such as large transformers and heat-sinked power semiconductors.

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                                                     3. Wire Wound Resistor:
       
Wire wound resistors are commonly made by winding a metal wire, usually nichrome, around a ceramic, plastic, or fibreglass core. The ends of the wire are soldered or welded to two caps or rings, attached to the ends of the core.

Applications of wire wound resistors are similar to those of composition resistors with the exception of the high frequency. The high frequency response of wire wound resistors is substantially worse than that of a composition resistor

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                                                                          4. Film Type Resistor:

      Thick film resistors became popular during the 1970s, and most SMD (surface mount device) resistors today are of this type. The resistive element of thick films is 1000 times thicker than thin films, Thin film resistors are made by sputtering (a method of vacuum deposition) the resistive material onto an insulating substrate.

      Thick film resistors may use the same conductive ceramics, but they are mixed with sintered (powdered) glass and a carrier liquid so that the composite can be screen-printed. This composite of glass and conductive ceramic (cermet) material is then fused (baked) in an oven at about 850 °C.

      Thin film resistors are usually far more expensive than thick film resistors. For example, SMD thin film resistors, with 0.5% tolerances, and with 25 ppm/K temperature coefficients, when bought in full size reel quantities, are about twice the cost of 1%, 250 ppm/K thick film resistors.

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5. Carbon Type Resistor:

Carbon composition resistors consist of a solid cylindrical resistive element with embedded wire leads or metal end caps to which the lead wires are attached. The body of the resistor is protected with paint or plastic. Early 20th-century carbon composition resistors had uninsulated bodies; the lead wires were wrapped around the ends of the resistance element rod and soldered. The completed resistor was painted for colour-coding of its value.

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                                                                         6. Fusible Resistor:

            

      Acts as a normal resistor under normal conditions but opens under a fault condition. The resistors act as a wire-wound resistor and a fuse, and are used in applications where precise control of fusing point and time lags are necessary. Similar types include a Fail-safe Fusible Resistor which combines a fuse and resistor in the same package.

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