Why the drain doesn't cause the body effect?

Status
Not open for further replies.
M

MelZ

Newbie level 3
Joined
Feb 13, 2014
Messages
4
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Visit site
Activity points
18
In the layout,the source and the drain are indentical,why we don't consider the body effect caused by Vdb>0?
 
Last edited:

I think...
Vd-Vb region is reverse polarized pn junction deeper than pn junction between source and bulk.So, changings between these two is more effective than drain and bulk.
There may be some other explanations but it should be first order cause..
 

The body effect changes the Vgs threshold so it effects that voltage for whichever terminal is used as the source. What type of effect do you think it could have on the drain?
 

crutschow said:
The body effect changes the Vgs threshold so it effects that voltage for whichever terminal is used as the source. What type of effect do you think it could have on the drain?
Click to expand...
such as when we calculate the vdsat,Vth should be larger than Vth(source) due to the body effect,namely Vdsat<Vgs-Vth(Source),why neglect the variation？
 


When we calculate the current,we neglect the Vth variations in the channel,why?
 

MelZ said:
In the layout,the source and the drain are indentical,why we don't consider the body effect caused by Vdb>0?
Click to expand...

Hi,

w.r.t NMOS, the drain will always be at higher potential than the source & body. Recollect that in CMOS IC, NMOS body is always connected to least potential.
In the figure, you can witness the drain-body diode is readily reverse biased.

Hence we are not bothered about the body effect w.r.t the drain. To correct, Vdb will be >0 always.

For more info **broken link removed**
 

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…