the meaning of vsat

what's meaning of vsat and it's the parameter of operating point in Cadence. I thought it is the over-drive voltage of the transistor. However, I find it's much larger than the (Vgs-Vth) and I'm not sure of my understanding！
Thank you for your help in advance！

there is no vsat but vdsat in op.It's vdsat=Vgs-vth is only valid in strong inversion. Someone choose Vdsat=4*UT for weak inversion. That's why vdsat is larger than vgs-vth

thx for your reply :0

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还要考虑速度饱和

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