what happens if we short drain-gate AND drain-sourse in MOS

[friendyboy]

Dear friends I want to know what happens when short drain-gate AND drain-sourse in MOS?how MOS behaves?

 

[satyakumar]

Re: what happens if we short drain-gate AND drain-sourse in

Hi,
The MOS will be in cut off region since the voltage b/w gate and source is zero in NMOSFET.

 

[ieropsaltic]

Re: what happens if we short drain-gate AND drain-sourse in

If you short the drain and the gate in a MOSFET, in the small signal analysis it becomes a diode-connected transistor i.e it is equivalent of a resistor of value 1/gm .Note that the diode connected MOSFET is always in saturation given that its Vgs is larger than Vth in other words it never operates in triode .If you short both the drain and source of a MOSFET and use them as one terminal along with the gate as another terminal you can use it as a MOS capacitor .One other application of the drain and source shorted together is at switches at capacitive switched ciruits to remove the charge injection .

 

[friendyboy]

Re: what happens if we short drain-gate AND drain-sourse in

Thank you very much "ieropsaltic" for giving me an elaborated explaination with applications.I don't know where can I find "helped me" button on EDA board.So I am expressing my thanks through reply.

 

[sxunxs]

Re: what happens if we short drain-gate AND drain-sourse in

ieropsaltic explains it well....

 

[abhisheksbox]

Re: what happens if we short drain-gate AND drain-sourse in

if drain and gate is shorted then MOS will behave as a diode connected load and it will never go to triode region and can be used as resistive load offering a resistance equal to 1/gm.

if drain and source is shorted then MOS capacitor in which SiO2 will behave as insulator.

 

[Junaid Alam]

Re: what happens if we short drain-gate AND drain-sourse in

it will act as a diode!