Why nmos is pull down

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But why this happen? Please add in additional information when necessary. Hi source of nmos can't connect to vdd because after connection its name is drain. I hope that it will be useful. Don't confuse , i can give the exact answer, as u said , when nmos and pmos are interchanged in the basic cmos inverter , the output swing will be from vdd-vth to vth. Say you have your Vdd connected to the drain of the nmos and the output is taken at the source.

The source voltage cannot go above Vdd-vth because when the source voltage reaches this limit there is no channel for current to flow from drain to source, and hence the source voltage cannot increase.

Someone correct me if this is not right. Click to expand Hi all, I will try to answer, if not corect feel free to coment. But Vt depends on body bias, mobility and doping concentration as well as channel length. As the body voltage increases there is increase in vbs and hence Vin needs extra effort to overcome the Vbs and to make the channel invert by sourceing electrons from source.

Active 6 years, 8 months ago. Viewed 48k times. Shubham Singh Shubham Singh 13 1 1 gold badge 1 1 silver badge 2 2 bronze badges. Add a comment. Active Oldest Votes. In relation to the Source pin For a NMOS part the Source pin must be connected at the low level, so when turned on the Drain pin can only "pull down" to that same low level. Nedd Nedd 5, 10 10 silver badges 13 13 bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name.

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