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The Dynamic Range of Broadband CMOS LNA with Noise Cancelling


M.S. Bychkov

Observed in modern communications systems trend of transition to broadband signals requires appropriate circuit solutions. The most acute problem is the development of the input low-noise amplifiers, made in CMOS technology. In this paper we first investigated research the dynamic range of several broadband CMOS input amplifiers, isolated in a separate subclass "with noise cancelling". Study was madding of the noise properties, carried out analytically and by computer simulation, the upper limit of dynamic range produced by simulation, using the Design Kit of the technology SiGe BiCMOS 0,25 um firm IHP (Germany). In the first phase evaluated the inertial properties of MOS transistors and the spectral densities of noise currents in the actual frequency range (1.6GHz). As a result, it was shown that, firstly, the inertial properties of transistors can be neglected, and secondly, in this frequency range the main source of the noise current can be considered noise current of the channel. This estimate is valid for low-resistance output impedance of the signal source, otherwise it is necessary to consider the induced noise gate and the correlation dimension. In the second phase was carried out analytical and computer calculation of the noise figures and computing analysis of the input compression point. Schemes were pointed to the same gain and matched to 50-ohm tract. Were evaluated: the accuracy of the analytical calculations, the partial contributions of noise sources of elements in the overall noise figure, the behavior of the compression point. In the third stage, we calculated the dynamic range. This study enabled us to formulate appropriate conclusions and proposals.

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