[SOLVED] NMOS transistor, question about Vgs

Status
Not open for further replies.
P

Pictou

Member level 1
Joined
Mar 19, 2013
Messages
34
Helped
5
Reputation
14
Reaction score
5
Trophy points
1,288
Activity points
1,570
Hello,

I would like to know what happens to a NMOS transistor when Vgs < 0. My problem is that in one of my schematic Vgs = -1.3 V. Will it break?

I tried to find the answer on the internet but nothing about Vgs < 0 for a NMOS (or Vgs > 0 for a PMOS)
On the forum, people talked about Tsividis book, but all links were dead.

Thank you for your help.
 

@Pictou: If Source & Body are at same potential,say Ground.
Then if Vgs > 0, NMOS operates normally, with a channel formed between Source & Drain in inversion.
If Vgs < 0, NMOS will be in accumulation & has no channel between Source & Drain. It will not conduct & all,it will be in cut-off but it shouldn't break-down.
If you make Vgs <<< 0,it reaches reverse-bias breakdown between Source & Body(p)
 
Last edited:
Reactions: Pictou

    P

    Pictou

    Points: 2
    Helpful Answer Positive Rating
Thank you very much for your help. I'll look for reverse-bias breakdown on google to learn more.
There is just something I don't understand, if source and body are connected at the same potential, why would they be in reverse-bias breakdown as they are connected to each other?

I'm not really familiar with these phenomena, can you advise me a book that could teach me this?

Thank you again.
 

@Pictou: The post#2 that i posted was for a simple MOSFET with no Zener diode.

But commercial MOSFETs usually have a big and powerful zener diode that will clamp the voltage and cause a lot of heat when it avalanches. The zener diode can also conduct a high current when it is forward-biased by the drain-source voltage going reversed.But even Zener Diode will only "absorb" it to an extent

"Operation & Modelling of MOS Transistor"Tsividis is very good.You were saying links are dead.It is available on Scribd for free
 
Reactions: Pictou

    P

    Pictou

    Points: 2
    Helpful Answer Positive Rating
Thank you for your help and the Scribd website, I didn't even know its existence. I will mark this subject as solved.
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…