Maks
Community Member
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Posts: 52
San Jose
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For Vbs until ~+0.7 V, everything goes as expected - Vt goes down, Id goes up.
After ~0.7V, you are strongly forward biasing source/body diode, and device goes into a crazy non-linear very high current regime. I am not surprised seeing Id going down - it's quite likely that the potential barrier for carriers to go form source to body/substrate becomes lower than the barrier to go into channel, so carriers are redirected from drain to bulk, hence reducing Id. There is no much meaning into biasing the device into this regime, even SPICE models may not be accurate here.
Max
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