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What is the relation of this DC parameters?

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huojinsi

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Utilizing spectre simulator and the models file of 5V standard CMOS process , a nmos transistor is simulated, and the DC operation point of this nmos transistor is printed in the picture. Under the condition of normal operation state, i have some doubts concerning its DC parameters:
1. Why is the "ibulk" current so big?
2. What is the relation of the DC parameters in the blue mark rectangle? why the Vdsat doesn't equate (Vgs-Vth)? According to the Vds,vgs and vth, how to calculate this vdsat and get 647.4mV?

Pls guide me! Any reply is very appreciated! Thks in advance!
 

Maybe "Vdsat" is the voltage of Drain at saturation,not the voltage of Drain-Source.
 

Hi teachers!
coming on, give me a reasonable explanation! If u have a formula of calculate, it is perfect! Thks!
 

does this tell us that the device is working above breakdown voltage?

because i never see people accept ibulk>100ua
 

Not above breakdown, but high enough so that impact ionization (hot electrons) is causing high substrate current. The device is probably intended for lower voltage, like 3.3.
Also note that the gds is pretty high here, due to the same effect.

Vdsat is the voltage calculated by the simulator that will be the approximate boundary between linear and saturation.
Vds is simply the drain-source voltage
Vgs is the gate source voltage
Vt is the threshold voltage

Hope that helps
 

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