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Testing a BJT accurately

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suhasm

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I am doing a study in which i am checking how exposing a BJT to certain conditions like extreme temperature etc will permanently affect its characteristics.

But , the problem is how to check?
I thought that using a curve tracer would be good.
I could trace the curve for Vbe VS IB before and after the test.
I could also do similar tests for Hfe , Vce VS IC etc.
Perhaps that would give me the results.

I only have a scope and a few multimeters at my disposal to carry out the check. Can anyone give any ideas?

It would be interesting to build an addon circuit that will allow the scope to be used as a curve tracer also.

Can anyone tell me how?
How can i generate the sweeping voltage to drive the component to be checked?
And how can i convert the current that the component outputs into a voltage which can be seen on the scope?
Should i use a op amp?
 

MikeMl

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A diode junction I/V curve tracer requires ja triangle sweep generator and a current-to-voltage converter. The voltage is used to drive the X axis of a analog scope while the output of the current-to-voltage converter drives the Y axis. Fancy tracers blank the Z axis during retrace.

A transistor Ic/Vc as a function of Ib curve tracer requires all of the above plus a current-step generator synchronized with the X sweep to drive the base.

To display dynamic hfe, you need a current sweep for the base (and a voltage proportional to the current to drive the X axis) and a constant voltage source with a current-to-voltage converter to drive the Y axis for the collector current. The hfe is the slope of the trace.
 

kchriste

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Mikebits

Well-Known Member
An octopus works as a poor mans curve tracer.

kd7rem's Octopus

I used one in the Navy many years ago. They do work fairly well.
 

Mikebits

Well-Known Member
To perform these test, I assume you have access to an environmental chamber, or at least a temp chamber.
 
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