Classification of Parametric Amplifiers and Converters

Abstract

Our study of background noise has shown that one of the methods of achieving very low-noise amplification consists in the use of a purely reactive amplifier, namely the parametric amplifier. Depending on the sign of the reactance used, one can expect that there would be two classes of parametric amplifiers : those with variable capacitance, and those with variable inductance. However, for technical reasons, the first are the only ones in practical use, whilst the second are still in the laboratory stage. In this chapter we will deal with the Manley and Rowe equations. These equations, in which the influence of the losses in the circuits and in the variable reactance are ignored, give to some extent the ‘conditions for the existence of a parametric amplifier’ and enable us to classify them qualitatively into different categories.