NPN negative collector resistance??

[darkfenriz]

at 0.2mA Ib

[OzMikeH]

Perhaps I am reading the graph wrong but the reistance is still greater than zero, the trend is that the resistance reduces very slightly with increasing voltage.

I think there are cases of negagitive resistance in theoretical applications, the standard unit of negative resistance is the "Mho"
(that may be a joke at my expense when I was an apprentice, I have never encountered it personally)

[phase_accurate]

It does inded show a negative dynamic resistance. But I assume it is an issue of plotting accuracy.
Otherwise it can be used to build oscillators (like tunnel diodes).

Regards

Charles

[darkfenriz]

Any semiconductor phenomena to judge if this is possible or not?

[Elvee]

Hi

A number of phenomena can cause a negative resitance; but generally, it's the other variety, ie an increase in current causing a decrease of the voltage across the device (avalanche+injection, diacs, etc).
This one is rather unusual, and I suppose Charles is right: it has to be an artefact. With an FET in the right conditions, it could be caused by thermal effects, but in a bipolar, it's rather the other way round.
LV

[PigletsDad]

I expect it is just a drafting mistake.

The curves for most bipolars in this region fit pretty well to constant Early voltage.

I would expect the product of output resistance and collector current to be roughly constant - this product is the Early voltage.

[darkfenriz]

Thank you guys, I thought I had lost my head....

[radtech]

Originally posted by OzMikeH
the standard unit of negative resistance is the "Mho"
(that may be a joke at my expense when I was an apprentice, I have never encountered it personally)

The term 'mho' was used in the past as the unit of electrical conductance, the reciprocal of resistance (1/R). The term has been replaced by 'siemens'.