What is the purpose of fingering MOSes ?

[coolguy]

the purpose of fingering

Can anyone please tell me whats the purpose of fingering the MOSes? Or what are are all the advantages of fingering the MOSes?

Thanks in advance.

 

[eda_freak]

purpose of fingering

finger reduces paracitic capacitances wrt to gate, thus we go for it..

 

[coolguy]

what is the purpose of fingering?

would you please explain how this happens, because even if you finger it,
the gate area remains the same.

 

[balance]

Re: purpose of fingering

finger reduce the resistance of gate and parasictic capacitance of drain(source).

 

[safwatonline]

purpose of fingering

what happen is that the area/perimeter of the drain/source diffusion decrease and hence the parasitic caps. decrease.

hello ballance, i have a question what is good in reducing the gate resistance, and how u concluded that ?

 

[aomeen]

Re: purpose of fingering

Hello all,

Reducing the gate resistance will reduce noise due to it, which dominates at very high frequencies,

the reduction is simply because the resistance of the fingers will be smaller "shorter", and all the fingers are in parallel, if the gate is connected from both ends the resistance is reduced by 1/4.

 

[yadhunandan]

I don't know how the capacitance reduces if i fingering...!!it is always said by fingering capacitance increases because fringe also contribute..

 

[D.A.(Tony)Stewart]

To reduce capacitance many short gate fingers in parallel has lower Cj = Capacitance of drain bottom pn junction per area (F/m^2)

For more explanation read below;
https://mixsignal.files.wordpress.com/2013/03/analog-layout.pdf

A more "politically correct" description should be MOSFET Gate finger design parameter.
MOSes could mean other things including "Mossies" which are mosquitoes.

 

[yadhunandan]

hi sir..
I have doubt that ..y the poly orientation is kept vertical and poly pitch is kept constant in short channel ??What is the significance of that..