On Noise Properties of Transistors and Amplifiers A Critical Review

It has been previously shown that the allowed values of minimum noise temperature T-min and N=R(opt)g(n) (Lange noise parameter) for any transistor have to satisfy inequality 1 <= 4NT(0)/T-min <= 2. Furthermore, it has been shown that in the useful frequency range for all transistors 4NT(0)/T-min approximate to 2. Experimental confirmations have been published for III-V FETs, HEMTs, HBTs (in several different technologies including GaN HEMTs), and CMOS devices. This paper examines the consequences of this fact for widely held and widely published assumptions in the treatment of noise in transistors and amplifiers, amongst those CMOS "gate induced noise" concept and CMOS "noise cancelling" amplifiers. It is shown that some long held concepts need to be reexamined. The discussion is illustrated with experimental data.