negative resistance BFU710 SiGe?

[bnevins]

The BFU710F data sheet figure 2 shows a negative resistance region.
Is this accurate, or is the data an artifact of device heating?

(they did not pulse the signals, but applied continuous collector voltage and the
transistor got hot, reducing the current at higher voltages).

https:
   xx   //www.rfmw.com/products/detail/     xx  bfu710f115-nxp/422514/

[T3sl4co1l]

Not sure why the munged link, you can just direct link the datasheet here...
https://www.nxp.com/docs/en/data-sheet/BFU710F.pdf
AFAIK, SiGe have extremely high Early voltage, or perhaps even a little bit negative.  It probably is a thermal effect as you suppose.

It's probably not an oscillation thing, like, parasitic oscillation while the curve tracer is working... it would likely look lumpier than that.

Tim

[MarkT]

Maybe its not negative resistance, its gain falling due to temperature rise?  Probably clutching at straws though, this is an exotic device compared to a 2N2222 or similar!