what kind of switch is better?

[icx]

system power is 2.8v.if one signal is 1.4v,what kind of switch is better
to transfer this signal?

a.nmos
b.pmos
c.npn
d.pnp

 

[extraord]

nmos. because nmos has better mobility.
actually cmos is the best.
well, for the logic process, because the bulk of nmos has to tie to VDD.
the equivilent Ron will be larger.

 

[jinxingsun]

CMOS is the best because the resistance is almost constant and low!

 

[dejunwang]

is your signal a DC or sinewave? what is its range?

 

[co_aa]

one of the major advantage of MOS versus bipolar is the high quality switch. So, you should choose from MOS. Since Vin=1.4v, Vgate=2.8v, so, it is better to use NMOS switch.

 

[moh2000]

MOS transistors are generally much better switches than Bipolar.

If your signal is a constant 1.4V (or changing below 1.4) then using an NMOS switch is more useful than using a PMOS or a CMOS switch,

BUT if signal > 1.4 then using PMOS will be better.

The only place where using CMOS is preferable is when the signal is rail to rail.