What will happen if we swap the transistors of an inverter?

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

What will happen if we swap the transistors of an inverter?

Post by Arvind » Wed Apr 09, 2014 3:46 pm

What will happen if we swap the transistors of an inverter?

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

Re: What will happen if we swap the transistors of an invert

Post by Narveer » Wed Apr 09, 2014 3:51 pm

If we swap the transistors of an inverter that means NMOS will acts as pull-up transistor and PMOS acts as pull-down. So

1. when input is HIGH then PMOS is in cut-off region and NMOS pull-up output to HIGH state. But output voltage will Vtn( i.e threshold voltage for NMOS) less than VDD. NMOS is BAD-1 switch.
2. When input is LOW then NMOS is in cut-off region and PMOS pull-down output to LOW state. But output voltage will Vtp( i.e. threshold voltage for PMOS) high than VSS. PMOS is BAD-0 switch.

So we have less output voltage swing and less noise margins.

Nmh(Noise margin in HIGH state)= Voh-Vih
Mml(Noise margin in LOW state)= Vil-Vol

Voh= Maximum output voltage available in high state
Vih= Minimum input that can be considered as high
Vil= Maximum input voltage that can be considered as low
Vol= Minimum output voltage available in low state

nikhilp
Posts: 3
Joined: Tue Apr 15, 2014 10:52 am

Re: What will happen if we swap the transistors of an invert

Post by nikhilp » Tue Apr 15, 2014 12:36 pm

A BAD BUFFER...thats all!

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