Spice mosfet dissipation

Trivial to do. Just place it off in the corner somewhere and compute VDS(MN3)*ID(MN3). Of course that's instantaneous power, requiring interval integration or filtering to get average.

In PSpice you can do that multiplication (and integration) in the post processor (PROBE) without needing a behavioral device in the schematic. There's also W(MN3) in PSpice. I suspect there are similar methods in LTspice.

...Jim Thompson

Can't you just do waveform math in the graph window?

Just label a waveform as V(vds)*I(Id)

You may have to negate the equation to show positive power.

In PSpice you sure can.

...Jim Thompson

Den onsdag den 22. oktober 2014 01.37.58 UTC+2 skrev John Larkin:

hold down ALT and you get a thermometer mouse pointer, click on the FET ?

-Lasse

Yes, that gives me a power graph, which I can integrate in any zoomed area to get average power.

Thanks.

The LT Spice "help" didn't.

In SuperSpice, you don't have to do anything at all. It all automatic. Place a test point on the component (instead of a pin or wire) and instantaneous transient power will be plotted. Move the mouse cursor over the component and the data display window at the bottom right of the main widow will display DC and Average transient powers. Cursor over wire or pin displays DC voltage and current.

:-)

Kevin Aylward

Is that symbol based (whether there's a MODEL or SUBCKT within), or only for MODELs?

Personally, I made my own EMETER, PMETER, SMETER, etc. components to deal with it. And a sampled filter component so I don't have to wait for RC filters to settle, or something like that. :)

Tim

Yes. It works the same whether a .model or .subckt.

It defaults with an available setup dialog with fields of integration start time and end time both equal to zero. End time at zero means integrate for the all of the data range.

There are other auto calculations as well :-)

Kevin Aylward