Re: How to implement long channel device (layout and schemat
jerryzhao said:
I draw the MOS in series (the SPICE model just has LMAX=10u) when I design circuit POR. Layout fold as schematics.
I don,t know why you use the such device in DAC. Which block you use such device.
Some question about draw the mos in series:
(1)for the series , all gate are connected, right?
(2)for all the series, the substrate all connected to vdd(if pmos) or just connect to the source to eliminate body-effect.
(3)if the series number of pmos with w/l is N , does it really equivalent to one pmos with w/(N*l)?
In my view, at least item(2) will make some difference in performance.
B.R
why I am using long channel devices?
I am calculating the min area needed for current source from the INL_yield and foundry mismatch-parameters. And since my design is 14-bit , the w/l ratio is very small for 1LSB, which cause the channel very large.
Hope my description makes things clear.