Physics - semiconductor diode.

endeavour

The problem is an experiment has to be set up to investigate how the breakdown voltage (which occurs by a large reverse potential difference is applied to the diode, and the diode then passes a large current) of a semiconductor diode is affected by temperature.


My problem is how can I vary the temp. of the diode in the range of minus 70 degrees C to 150 degrees C, whihc is what the question asks for,

I think I can get a range of about -10 celcius to 70 degrees , but I also want to ask whether it is safe to submerge the diode in hot water (which will be heated by a bunsen burner)?

Also how can I set up a circuit so that the breakdown Voltage is calculated BUT also avoid large currents (which would cause damage to the diode when breakdown occurs) <- this is probably the most important bit.
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THANKS to anyone with any ideas and suggestions!

xanthym

Dry ice can attain approx (-60 degC). Liquid nitrogen can attain approx (-200 degC). A standard kitchen oven can be preheated (and then the heat turned off) to almost any temperature up to (+200 degC).

For the diode "reverse-bias" voltage breakdown test, place the diode in series with a current limiting resistor "R". During the test, monitor the voltage drop across R. Before breakdown, very little voltage will drop across "R" (diode limits current). After breakdown, you will see a noticeable change, and R will limit the current thru the diode.


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endeavour

Thanks very much for your help.

endeavour

by voltage drop, do you mean the voltage across R gets more negative, as the breakdown voltage is approached?

xanthym

The voltage drop magnitude across R will increase when breakdown occurs since more current will flow through R. Whether you measure it positive or negative depends on how you've connected your meter. Presumably you'll connect your meter with the (+) lead on the terminal of R closest to the (+) voltage source. In that case, the reading will change from near 0 before breakdown to a larger (+) reading after breakdown.