The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Design >> Analog Design >> MOS Cap region of operation
https://designers-guide.org/forum/YaBB.pl?num=1216101021

Message started by jiesteve on Jul 14^th, 2008, 10:50pm

Title: MOS Cap region of operation
Post by jiesteve on Jul 14^th, 2008, 10:50pm

MOS Caps can either be operated in accumulation or inversion... What are the pros/cons of each?

Title: Re: MOS Cap region of operation
Post by neoflash on Aug 16^th, 2008, 9:48pm

MOSCAP in inversion region is more stable with frequency and is lower in loss.

Accumulation region capacitance will reduce with higher frequency. Also the loss is higher.

Title: Re: MOS Cap region of operation
Post by vivkr on Aug 17^th, 2008, 10:58pm

neoflash wrote on Aug 16^th, 2008, 9:48pm:

MOSCAP in inversion region is more stable with frequency and is lower in loss.

Accumulation region capacitance will reduce with higher frequency. Also the loss is higher.

Hi neoflash,

I would have imagined the reverse to be true. Atleast the textbook model shows you 2 curves for the inversion region, the high-f and low-f ones, whereas for accumulation, this is not the case. Are you considering the losses due to the parasitic resistance etc. that come into play with the accumulation cap (which the textbook does not consider)?

Regards,
Vivek

Title: Re: MOS Cap region of operation
Post by nanion on Aug 20^th, 2008, 8:18am

Hi,

I am also of the opinion that in accumulation MOS cap is more stable then inversion mode.

About the loss not sure but I guess the bottom layer is a p-type (hole) conduction in accumulation as compared to an electron conducive (NMOS Cap assumed) with electron reservoir (n+ regions) in inversion mode. So it could be lossy but still not positive though.

--