PMOS as pullup & NMOS as pull down. why?

Device Physics doubts related to diode, transistor, BJT, MOSFET, JFET.
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Arvind
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Joined: Wed Apr 09, 2014 3:11 pm
Location: Noida, India

PMOS as pullup & NMOS as pull down. why?

Post by Arvind » Wed Apr 09, 2014 3:45 pm

why PMOS is used as pullup device and NMOS is used as pull down device?

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Narveer
Posts: 59
Joined: Tue Apr 08, 2014 11:29 am
Location: Bangalore, INDIA

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

Post by Narveer » Wed Apr 09, 2014 3:57 pm

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.

viewtopic.php?f=11&t=6

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