Why Does Base Current Start at 20uA at the Bottom in NPN Curve Tracers?

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SUMMARY

The discussion centers on the behavior of base current in NPN curve tracers, specifically addressing why base current starts at 20uA at the bottom of the graph rather than at the top. It is established that for PNP transistors, both collector current (Ic) and collector-emitter voltage (Vce) are zero at the top right corner. The participants conclude that the representation of base current in the curve tracer may be incorrectly labeled, suggesting that 20uA should correspond to the smallest Ic trace at the top of the graph.

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sandy.bridge
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Hello,
Hoping this can be cleared up quickly as I have my final exam in 1 hour. My question is for the attached image. I know for pnp transistors that ic=0, and Vce=0 at top right hand corner. However, one thing I don't understand is why the base current starts at 20uA at the bottom, rather than at the top. Help is greatly appreciated!
 

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Probably too late for your exam, but it looks wrong to me. 20uA should be the top (smallest Ic) trace, and Ib should step to larger values at the larger Ic values.
 
That's what I thought. Looks like whoever marked it was not paying attention.
 

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