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Homework Help: Differential Thermocouple Amp

  1. May 22, 2008 #1
    Hello, I would like to build a Voltage Amplifier, I did one with 2 Transistors but doesn´t work, it doesn´t amplify.
    Do you know pleas how to build an Amplifier with transistors and resistors? an easy one with no more then 2 or 4 transistors please. Do you all think it´s possible?
  2. jcsd
  3. May 22, 2008 #2


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    Welcome to PF.

    Sounds like you want to build an amp out of separate components.
    What do you know about hFE, biasing and perhaps negative feedback?

    For some samples, you could try to google the subject -> one transistor amplifier
    Last edited by a moderator: May 22, 2008
  4. May 22, 2008 #3
    See "Voltamp.jpg" please. It doesn´t work, two wires of different materials, united at the one end, if you touch that point the voltmeter should amplify the 0,001 Volt that is caused by the different temp.

    Don´t know your terms Notime, sorry, and transistor amp. with AC don´t wanna study. I am doing DC, stop.


    Attached Files:

  5. May 22, 2008 #4


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    Staff: Mentor

    I split these posts out of the old thread they were appended to, and started this new thread. I also moved the thread out of EE to here in the Homework Help forums.

    Welcome to the PF, Ciani. That is a differential amplifier that should give you a differential output voltage that varies with the thermocouple temperature. What voltages do you measure at the various nodes in the circuit?
  6. May 22, 2008 #5
    Thanks a lot,
    The circuit should measure 1 mV changes.
    One of the two wires during transport has gone broken, transistors are type B547C but I don´t think it is relevant by such a circuit.


    Attached Files:

    Last edited: May 22, 2008
  7. May 22, 2008 #6


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    At this point, I'm not sure what your question is.
    You can use the schematic you posted before as a guide to reconnect the wire.

    Good luck.
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