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TMP461: How do I choose BJT or diode for a temperature sensor

Prodigy 130 points

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Part Number: TMP461

Hi e2e,

I read some temperature sensor, it explains that we should to use different type sensor using PTC, NTC, TMP IC for application.

But, How do active component influence temperature sensor? . For example, TMP641 block diagram has an internal BJT for sensing temperature, why it does use BJT rather than diode?

Thus, how do I choose BJT or diode for a temperature sensor? 

Thanks.

  • Hi,

    In most cases a thermal diode is BJT configured to function as a diode as you can see in Figure 18 on page 23 of the TMP461 datasheet.  The TMP461 uses the characteristics of a BJT and senses the change of Vbe voltage due to temperature and biasing current to calculate an accurate temperature.  

    Choosing which type of temperature sensor is dependent on your system constraints and needs (Voltage Range, Temperature Range, Accuracy, Cost,  etc...).  

    The TMP461 is a remote temperature sensor which has a local digital temperature sensor as well as inputs for a remote BJT to be connected to monitor 2 separate locations. We recommend using a 2N3904 (NPN) or 2N3906 (PNP) for the remote connection.  

    Our ebook is a great starting point in learning how temperature sensors work and to figure out which type to use depending on the application.

    http://www.ti.com/lit/ml/slyy161/slyy161.pdf

    Thanks,

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