choosing mosfets over bjts in lna design

who said , that the BJT can't be used as LNA ,
the noise figure of the BJT is much lower than the MOS , the gain of the BJT is much higher than the CMOS

the linearity is lower than the MOS , i think BJT matching is harder

but BJT till now used as LNA , in the GHz range

check www.nxp.com , www.avagotech.com


khouly

many LNA products are made of BJT

yeah , and even in hgh frequency the BJT outperform the CMOS

khouly

BJT perform better than cmos

Besides what has already been said, BJTs also have a lower 1/f noise. I don't think it is any harder to match a BJT vs. a MOSFET, from what I have experienced.

So, what is the common way to match a BJT to 50Ohms with a good NF?

if u are talking about integrated BJT , one common way is to use degenration inductor , to make the input impedance high , and also increase the Ropt , for minimum noise figure , the use sreise coil with gate , with this u can get good NF performance with BJT

if discreet , u can use microstrip matching network , also the discrete BJT's are optimized so that there input impedance is higher than integrated ones


khouly

Cost of production is an issue in choosing MOS..