On noise properties of transistors and amplifiers a critical review

Abstract

It has been previously shown that the allowed values of minimum noise temperature T min and N=Roptgn (Lange noise parameter) for any transistor have to satisfy inequality 1:S4NTo/Tmin:S2. Furthermore, it has been shown that in the useful frequency range for all transistors 4NTo/Tmin"'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.

Light activation of noise at microwave frequencies: a study on scaled gallium arsenide HEMT's

“…As a complement to our previous studies, the present paper is aimed at analysing in details the characteristics of light activation of such excess noise by employing two different noise models, i.e. the noise temperature circuit model and the analytical noise model based on K g , K r and K c coefficients (hereinafter referred to as KGCR model) [13][14][15][16]. The devices under test are lattice-matched GaAs HEMT's having 0.25 μm gate length and 100-200-300 μm gate widths, whose DC, linear scattering and noise parameters had been previously measured in dark conditions and under continuous wave (CW) light exposure at 650 nm.…”