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A thermistor is a semiconductor resistor whose resistance varies significantly with temperature, making it useful as a temperature sensor or for controlling current. There are two main types: negative-temperature-coefficient (NTC) thermistors, which decrease in resistance with increasing temperature, and positive-temperature-coefficient (PTC) thermistors, which increase in resistance. Thermistors are commonly used in applications such as inrush current limiting, temperature sensing, and overcurrent protection, with operational temperature ranges typically between -100 and 300 °C.

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34 views2 pages

Ich Will

A thermistor is a semiconductor resistor whose resistance varies significantly with temperature, making it useful as a temperature sensor or for controlling current. There are two main types: negative-temperature-coefficient (NTC) thermistors, which decrease in resistance with increasing temperature, and positive-temperature-coefficient (PTC) thermistors, which increase in resistance. Thermistors are commonly used in applications such as inrush current limiting, temperature sensing, and overcurrent protection, with operational temperature ranges typically between -100 and 300 °C.

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Ілюша Вільчик
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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A thermistor is a semiconductor type of resistor in which the resistance is strongly dependent on

temperature. The word thermistor is a portmanteau of thermal and resistor. The varying resistance
with temperature allows these devices to be used as temperature sensors, or to control current as a
function of temperature. Some thermistors have decreasing resistance with temperature, while
other types have increasing resistance with temperature. This allows them to be used for limiting
current to cold circuits, e.g. for inrush current protection, or for limiting current to hot circuits, e.g. to
prevent thermal runaway.

Thermistors are categorized based on their conduction models. Negative-temperature-


coefficient (NTC) thermistors have less resistance at higher temperatures, while positive-
temperature-coefficient (PTC) thermistors have more resistance at higher temperatures.[1]

NTC thermistors are widely used as inrush-current limiters and temperature sensors, while PTC
thermistors are used as self-resetting overcurrent protectors and self-regulating heating elements.
An operational temperature range of a thermistor is dependent on the probe type and is typically
between −100 and 300 °C (−148 and 572 °F).

Thermistor

Negative-temperature-coefficient (NTC) thermistor,


bead type, insulated wires

Type Passive

Working principle Electric resistance

Electronic symbol

Thermistor or varistor symbol[2]

Types

[edit]

Depending on materials used, thermistors are classified into two types:


• With NTC thermistors, resistance decreases as temperature rises; usually because electrons
are bumped up by thermal agitation from the valence band to the conduction band. An NTC
is commonly used as a temperature sensor, or in series with a circuit as an inrush current
limiter.

• With PTC thermistors, resistance increases as temperature rises; usually because of


increased thermal lattice agitations, particularly those of impurities and imperfections. PTC
thermistors are commonly installed in series with a circuit, and used to protect against
overcurrent conditions, as resettable fuses.

Thermistors are generally produced using powdered metal oxides.[3] With vastly improved formulas
and techniques over the past 20 years[when?], NTC thermistors can now achieve accuracies over wide
temperature ranges such as ±0.1 °C or ±0.2 °C from 0 °C to 70 °C with excellent long-term stability.
NTC thermistor elements come in many styles [4] such as axial-leaded glass-encapsulated (DO-35, DO-
34 and DO-41 diodes), glass-coated chips, epoxy-coated with bare or insulated lead wire and surface-
mount, as well as thin film versions. The typical operating temperature range of a thermistor is
−55 °C to +150 °C, though some glass-body thermistors have a maximal operating temperature of
+300 °C.

Thermistors differ from resistance temperature detectors (RTDs) in that the material used in a
thermistor is generally a ceramic or polymer, while RTDs use pure metals. The temperature response
is also different; RTDs are useful over larger temperature ranges, while thermistors typically achieve
a greater precision within a limited temperature range, typically −90 °C to 130 °C.[5]

Basic operation

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