1.
You can find some information about FET models in these publications.
https://core.ac.uk/download/pdf/17180215.pdf
http://epubs.surrey.ac.uk/805122/1/PID1256805-1.pdf
http://epubs.surrey.ac.uk/803447/1/6565_final.pdf
2.
The datasheet DC parameters can differ from those obtained by simulations on several reasons.
- datasheet specs provide typical values. The model parameters may be based on different device instances. Generally, most critical simulated parameters fit the specified min-max range.
- the model has been optimized to fit measured data within some characterization limits. The priority is given to fit measured RF performance. The values beyond the characterization limits are extrapolated.
- Apparently, MRF300AN model parameters has been characterized at VGS<4V. The model mis-predicts drain current at higher VGS value. You can see it on simulated IDS vs VGS plot. The drain current increases from VGS 0V to 4.5V. It decreases at VGS>5V and it doesn't reach maximum at VGS=10V. This is unexpected behavior - the drain current must increase vs gate voltage (excepting thermal self-heating effects).
Note. This mis-prediction doesn't affect simulation of MRF300AN in it's normal operating mode as class AB amplifier. Typical peak current in this mode is about 12A that doesn't require VGS more than 4V.
The last note. Self-heating effects are important when doing DC simulation. In practice, DC characterization can be performed in pulsed mode to remove the influence of self-heating. The same effect can be obtained in simulation if you set model parameter RTH=0. You can see the difference of IDS vs VDS curves from the previous chart.
Best Regards
Pavel
NXP TIC
1.
You can find some information about FET models in these publications.
https://core.ac.uk/download/pdf/17180215.pdf
http://epubs.surrey.ac.uk/805122/1/PID1256805-1.pdf
http://epubs.surrey.ac.uk/803447/1/6565_final.pdf
2.
The datasheet DC parameters can differ from those obtained by simulations on several reasons.
- datasheet specs provide typical values. The model parameters may be based on different device instances. Generally, most critical simulated parameters fit the specified min-max range.
- the model has been optimized to fit measured data within some characterization limits. The priority is given to fit measured RF performance. The values beyond the characterization limits are extrapolated.
- Apparently, MRF300AN model parameters has been characterized at VGS<4V. The model mis-predicts drain current at higher VGS value. You can see it on simulated IDS vs VGS plot. The drain current increases from VGS 0V to 4.5V. It decreases at VGS>5V and it doesn't reach maximum at VGS=10V. This is unexpected behavior - the drain current must increase vs gate voltage (excepting thermal self-heating effects).
Note. This mis-prediction doesn't affect simulation of MRF300AN in it's normal operating mode as class AB amplifier. Typical peak current in this mode is about 12A that doesn't require VGS more than 4V.
The last note. Self-heating effects are important when doing DC simulation. In practice, DC characterization can be performed in pulsed mode to remove the influence of self-heating. The same effect can be obtained in simulation if you set model parameter RTH=0. You can see the difference of IDS vs VDS curves from the previous chart.
Best Regards
Pavel
NXP TIC
