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PMOS as pullup & NMOS as pull down. why?

Posted: Wed Apr 09, 2014 3:45 pm
by Arvind
why PMOS is used as pullup device and NMOS is used as pull down device?

Re: PMOS as pullup & NMOS as pull down. why?

Posted: Wed Apr 09, 2014 3:57 pm
by Narveer
NMOS can pull-down output to 0V but it can pull-up maximum to VDD-Vtn. So it is bad-1 and good-0. PMOS can pull-up output to VDD but it can pull-down to Vtp. So it is bad-0 but good-1 where Vtn,Vtp are threshold voltage for NMOS and PMOS respectively. Also check below link.

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