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Problems with transistor operation point info in transient analysis

greywanderer

I want to look at transistor operating points during a transient simulation. So I used "*:oppoint" in the save statement. The plot below shows a transistor's vds, vgs, drain and gate voltages(gnd/source is the net 0).



It seems like there may be some problems with way the vds, vgs are reported.

  • It's a bit hard to see what's going on here, but one possibility is that the transistor is flipped (hence the sign difference), and the other is that this is an inline subckt with other components around it. The "actual voltages" are probably plotted at the outside pins of the transistor, whereas the vds/vgs are reported from the inline device. 

    Without seeing it, I can't be sure of a precise explanation. If it worries you, contact customer support so that somebody can take a proper look.

    Regards,

    Andrew

  • in reply to Andrew Beckett

    I checked to see if the S/D swap button was checked for this transistor. It was not. Also, if it was a flip, we should see -9.8uv on the other vertical marker than +9.8uv. But you maybe right about inline circuits. Let me check.

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