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I have recently bought a simple curve tracer made by Leader. It is connected to the scope to use as a monitor. One of the transistors shows normal curves (7), the other one is skipping a few curves (shows 3). What does that mean?
These curves are upside down compared to how they are normally shown. The second curve is with a transistor with a much higher gain, so the collector current is much higher per step (in your display sitting further down the screen) and the 4th and 5th step are off the screen at the bottom.
Frank
Negative curve is for PNP.. step size is programmable The bigger the output steps indicates higher hFE for that step input. hFE drops with increased current. Flat slope means perfect current source, non flat indicates leakage on current source. step space on output converted to mA divided by step size on input = hFE at that point vs Vce.. A very linear device has flat curves. A very high gain device has big steps on output.. For more resolution,, reduce input step size (mA) and number of steps.
step size in this case is 10uA, I should make it smaller? This is the minimum of the tracer... I do have an external bias input (asked about generating a stable low current like that on a different post).
no 10uA is fine, then just increase vertical scale with 10 steps as long as SOA is not exceeded on part.
Wounded parts tend to look more leaky.. with more slope on the curve.
An ideal current amplifier {with stepped current controlled input} has a current source output and is flat with infinite impedance.
I saw on a curve tracer manual how to measure the non-linearity of a device using the technique shown in the attached diagram, however I can not understand how they select the operating load line the crosses the rated operating voltage. Is this Vcbo? In the case of my transistor that's 30V and the curves are cutting off before that.
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