In this paper, a noise revision of an InAlAs/InGaAs/InP psoeudomorphic high electron mobility transistor (pHEMT) in presented. The noise performances of the device were predicted over a range of frequencies from 1GHz to 100GHz. The minimum noise figure (NFmin), the noise resistance (Rn) and optimum source impedance (Zopt) were extracted using two approaches. A physical model that includes diffusion noise and G-R noise models and an analytical model based on an improved PRC noise model that considers the feedback capacitance Cgd. The two approaches presented matched results allowing a good prediction of the noise behaviour. The pHEMT was used to design a single stage S-band low noise amplifier (LNA). The LNA demonstrated a gain of 12.6dB with a return loss coefficient of 2.6dB at the input and greater than -7dB in the output and an overall noise figure less than 1dB. Keyword:InAlAs INTRODUCTIONThe InAlAs/InGaAs/InP psoeudomorphic high electron mobility transistors (pHEMT) have exhibited excellent performances in terms of noise figure compared to MOSFET devices at RF and microwave fields [1]. In addition, they are mostly used in the design of low noise amplifiers [2-4] and proven to be more advantageous that the AlGaAs/InGaAs pHEMTs [5].Advanced circuit design that uses pHEMT, needs precise and accurate noise models, especially for their application in low noise MMIC. Many noise models have been reported in the literature: the wellknown Fukui's model [6], the equivalent noise temperature model by Pospieszalski [7] and the flicker noise model for HEMTs [8]. Many approaches on HEMT's noise parameters characterization ware investigated [9][10][11].In 1974, R.A. Pucel proposed a charge control based approach for a noise model in FET devices, the model is known as the PRC noise model [12]. Later in 1988, the model was used for HEMT devices in [13] and later improved by Zhi [14] where they included, in the PRC model, the temperature coefficients in order to calculate precise noise parameters for HEMTs.In this paper, we try to predict the noise performances at high frequency of an InAlAs/InGaAs/InP pHEMT by extracting the basic noise parameters using two approaches: a physical modelling and a mathematical modelling. This work is organized as follow: first, we discuss the different sources of noise in the pHEMT devices. Then, we make use of ATLAS from SILVACO TCAD suit, to simulate the noise behavior of a fabricated InAlAs/InGaAs/InP 250 nm gate length pHEMT. Next, we describe the analytical model based on the 2-port small-signal equivalent circuit of the device mentioned before and we calculate the

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