NOISE in BJT and MOSFET

[analog_newbie]

why noise is more in BJT compared to MOSFET ?
I wanted to know the physics behind it.

 

[alperuslu]

There is no general situation. Some frequencies BJT has lower noise than mosfet and vice versa. It depends on device characteristics.

 

[flatulent]

Generally, at the lowest frequencies JFET is lower, then at higher frequencies BJT is best and at still higher GaAs is best. Ordinary MOSFET is generally worse than these three at any frequency. They are used because the IC process on silicon has the smallest number of masking steps for MOSFETs. This smaller masking steps causes or results in lower processing costs and higher yield.