Open drain NMOS - how does it work?

[crazy4analog]

Open drain NMOS

usually in circuit design an interrupt signal is through an open drain nmos. In applications a pullup resistor is connected on this open drain to indicate an interrupt.

I would like to know how does this open drain NMOS works. I tried looking online, however, could not comprehend.

Thanks

 

[aProgrammer]

Open drain NMOS

https://en.wikipedia.org/wiki/Open_collector

https://en.wikipedia.org/wiki/Pull-up_resistor

 

[JoannesPaulus]

Open drain NMOS

When the gate of the open drain goes high, the drain is sinking current through the pull-up resistor and therefore it goes low. When the gate is low, the transistor is switched off (no current) and the pull-up resistor will set the voltage to high.

I hope it helps!

 

[crazy4analog]

Re: Open drain NMOS

Thanks for the reply!!

In both these cases, does NMOS operate in saturation(active) or linear(triode) region?

And how is it biased?

 

[JoannesPaulus]

Open drain NMOS

it is on-off, no bias needed.