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-   -   Differential Thermocouple Amp (http://www.physicsforums.com/showthread.php?t=236581)

 Ciani May22-08 07:19 AM

Differential Thermocouple Amp

Hello, I would like to build a Voltage Amplifier, I did one with 2 Transistors but doesnīt work, it doesnīt 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 itīs possible?
Ciani

 NoTime May22-08 10:35 AM

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

 Ciani May22-08 10:47 AM

1 Attachment(s)
See "Voltamp.jpg" please. It doesnīt 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.

Donīt know your terms Notime, sorry, and transistor amp. with AC donīt wanna study. I am doing DC, stop.

Ciao.

 berkeman May22-08 10:54 AM

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?

 Ciani May22-08 11:18 AM

2 Attachment(s)
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 donīt think it is relevant by such a circuit.

Ciao

 NoTime May22-08 03:21 PM

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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