Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Temperature sensor with BJT?

  1. May 23, 2015 #1
    Hey there, I want to build a simple temperature sensor using a BJT (BC547, 2N2222, or similar). I'm not sure how should I do that. My first thoughts where: measuring the Vbe, using around 9v to 12v as Vcc, the transistor with common-emitter; then just wrap the transistor in plastic or something and dipping it in warm water (measuring water temperature with a simple thermometer).
    This way I could just plot Vbe vs Temperature (from 10°C to 80° maybe), later I could plug it to an arduino or something to get the actual temperature value
    My questions are about, which resistors to use for the common-emitter polarization of the BJT? , and most importantly, How could I measure Vbe? I was suggested to use 2 opamps, one to measure the voltage difference between base and emitter and the second one to amplify the signal of the first opamp, but I'm not sure about this method.
    Thanks for your help :v I'm not very good at this. Need help!!! :)
    Should I try to measure another thing? Ic? Ie? any ideas? :)
  2. jcsd
  3. May 24, 2015 #2


    User Avatar

    Staff: Mentor

    Try a google search, "using transistor as a temperature sensor"
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook