Types of Thermistors - Using the Right Thermistors to Protect Electronic Components

What is a Thermistor?
We all must have heard the term resistor, an electronic component that is used to restrict the flow of electric current through the circuit. Similar to the resistor, there is another electronic component, or rather a special type of resistor, known as thermistor, whose resistance changes significantly with respect to temperature. Generally, the resistance of most of the metals increases with increase in temperature, while thermistors respond contrarily. Rather than increasing resistance with the temperature, the resistance of thermistors decreases with increase in temperature. This principle of thermistor is used to measure the temperature of the body when connected to the electrical circuit.

Types of Thermistors
Thermistors are available as negative temperature coefficient (NTC) and positive temperature coefficient (PTC). They are manufactured to protect electronic components from a surge and excessive inrush of current. These NTC and PTC thermistors are proving tremendously reliable and inexpensive, but the key to a successful outcome is identifying which components are best suitable for particular applications. First, let us figure out what work these components perform.

A thermistor exhibits a substantial change in resistance through significant change in its body temperature. The resistance of PTC increases with increase in temperature and that of NTC decreases with increase in temperature. Both kinds of thermistors offer unique features, which makes them perfect for specific sensor applications.

Negative Temperature Coefficient Thermistor
Negative temperature coefficient thermistors are designed to control the high and sudden inrush of current so to protect electronic components. This characteristic of NTC thermistors makes them ideal for high-rated transformers with slow-starting loads. NTC Thermistors are used in devices like compressors, huge vacuum cleaners, conveyor belt drives, and other devices.

Positive Temperature Coefficient Thermistor
Positive temperature coefficient thermistors are manufactured to protect other electronic components from short-circuiting. It protects applications from damage caused by continuous excessive current or short-circuit that might occur in the electronic device. Mostly, PTC thermistors are used to restrict the risk associated with faulty link-circuit power semiconductors and capacitors.

Applications of Thermistors
1. PTC thermistors are used as a heater in the automotive industry to heat up the diesel in diesel engine in cold weather conditions.
2. PTC thermistors are used as current-limiting components for circuit protection.
3. NTC thermistors are used to monitor the temperature of the incubator.
4. They are used in the hot ends of 3D printer. Thermistors monitor the heat  produced and allow its control circuitry to maintain a constant temperature for melting the plastic filament.
5. They are also used in modern digital thermostats and battery packs to monitor its temperature while charging.

When it comes to choosing one, NTC thermistors are available in a wide range. PTC thermistors often perform the similar function across the board, while NTC thermistors also perform the similar function, but they function at varying temperature and current. NTC thermistors are categorized into two broad groups based on how the electrodes are connected to the ceramic body. The first group of NTC thermistors is denoted by bead type thermistors. Each bead type thermistor has a platinum alloy lead wire connected directly to the ceramic body. The second group uses metalized surface contacts, which offer leads, radial leads, axial, or no lead for surface mounting. The wide range of different NTC thermistors by Analog Technologies, Inc made them suitable for almost any application.

It is very critical to limit the surges, whether sudden or continuous, to protect electronic components within any equipment that contains circuit. To protect these components from both excessive continuous current and sudden inrush of current, the best option would be using the combination of NTC and PTC thermistors.


  1. I definitely respect and am grateful for your point on every single object about thermistors. thanks for sharing
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  2. PTC thermistors can be used as current-limiting devices for circuit protection, as replacements for fuses. NTC thermistors are used as resistance thermometers in low-temperature measurements of the order of 10 K. Actually these are very useful thermistors to resist the current. Thank you.

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