What Is the Difference Between NTC and PTC Thermistors

“Thermistor” is the name given to thermally sensitive resistors whose primary role is to show an accurate change in electrical resistance in response to changes in the surrounding temperature. They are made of semiconductor materials which exert less resistance in either increased or decreased temperatures depending on the device. In addition to being very small for use in tight spaces, thermistors respond quickly to temperature changes, making them the most sensitive temperature sensors out there. Both negative temperature coefficient (NTC) and positive temperature coefficient (PTC) thermistors’ values change when exposed to shifts in temperature, but the way in which they are impacted makes them suited for different applications.

For NTC thermistors, as temperature increases, the resistance drops from high to low, and allows current to pass through. In a circuit, this can be used to limit in-rush current or a sudden, large amount of current drawn by an electrical device when  first turned on. The in-rush can be naturally limited as the thermistor will automatically heat up when a current is applied to it, accepting a large flow before falling naturally to allow normal current flow. Because of this capability, NTC thermistors are the most commonly used type of device for temperature sensing applications where the initial temperature and current flow may be high. For PTC thermistors, as temperature rises, resistance increases to block over-current. For this reason, they are often used as a fuse which can let out a controlled amount of electrical current to avoid damaging a system.

NTC thermistors are used in a wide range of industries that require high accuracy when it comes to temperature. Some of their functional applications include temperature compensation, in-rush current limiting, temperature measurement, and fluid level gauging. Typical applications for PTC thermistors are in self-regulating heaters, over-current protection systems, time delay devices, and applications regarding motor starting and fluid level gauging as well. Both NTC and PTC Thermistors display measurements that are accurate and repeatable, but also highly nonlinear, meaning that they do not represent a straight line or gradual change on a display; instead, they adjust with every minimal change. Therefore, more circuitry is required to linearize the output. It should also be noted that the maximum temperature that an NTC thermistor can measure is 130. However, the transition temperature of most PTC thermistors is greater, between 60 and 120 . Though, there are also specially manufactured options that can switch as low as 0 or as high as 200 which are available.

In conclusion, thermistors are temperature-sensitive resistors which can be used for measurement or to control circuitry for shifts in temperature or current. As a result, they can be helpful tools in a variety of sectors, including as equipment in automotives, heating and air conditioning systems, commercial and military aviation, and much more. For access to a wide inventory of aviation, NSN, and electronic parts, explore our various offerings on RFQ Experts. As a part of the ASAP Semiconductor family of websites, RFQ Experts provides our customers with access to a vast inventory of parts, all from trusted manufacturers on our Approved Vendor List (AVL). To start the process today and see why so many choose RFQ Experts for their procurement needs, you may browse our catalog of available items on our website. To get a competitive quote for your comparisons on any of the parts we offer, simply send us a completed RFQ form available on our website and expect to receive a response tailored to your specific needs in 15 minutes or less!


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