Why do we need both PMOS and NMOS transistors to implement a pass gate?

Why do we need both PMOS and NMOS transistors to implement a
pass gate?

Question Posted / markus

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Why do we need both PMOS and NMOS transistors to implement a pass gate?..

Answer / eyeman

Any logic gate can be constructed using pMOS and nMOS
transistor. nMOS being negatively doped silicon, rich in
electrons while pMOS is positively doped silicon, rich in
holes. Thus pMOS transistors are great at transmitting a
logic 1 voltage without signal loss, but the same cannot be
said about logic 0 voltages. Having 0 V at one side of a
conducting pMOS transistor yields a voltage at the other
side somewhat higher than 0 V. nMOS transistors are good to
pass logic 0 but not so good at passing logic 1. Thus the
best possible transmission behavior can be obtained by
combining both kinds of transistors. This is the trick in
pass gate.

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Why do we need both PMOS and NMOS transistors to implement a pass gate?..

Answer / pushpa

both are not perfect at 0 or 1,pmos is perfect of 1 but not 0,so nmos is perfect of 0 not 1..so we are use the both

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Why do we need both PMOS and NMOS transistors to implement a pass gate?..

Answer / akshay aggarwal

nmos output is inverted.for eg.-
if we have to make y=a+b
we will design it using nmos....but we get the output
ybar = a + b
to get y instead of ybar we use a complementary pmos circuit

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