Patent ID: 8212615
Filing Date: 2012-07-03
Classification: H03G

Abstract:
1. A variable-gain amplifier circuit comprising: an input matching circuit that generates a predetermined matching impedance for a preceding output impedance; a conductor circuit that outputs a current proportional to conductance with respect to an input voltage applied through the input matching circuit and a voltage between a reference voltage terminal and the conductor circuit; at least one variable-load circuit having a function for converting an input current applied to the conductor circuit to a voltage signal and capable of controlling a conversion factor for the current-to-voltage conversion; an output matching circuit that is connected to the variable-load circuit to generate a predetermined matching impedance for a succeeding input impedance; and a stabilization circuit that is connected to the variable-load circuit to cause resistive power loss within a specific frequency range; wherein the variable-load circuit includes three reactance function elements, at least one of the three reactance function elements being capable of changing a reactance value thereof; wherein an input terminal of the input matching circuit is used as an input terminal of the variable-gain amplifier circuit, and an output terminal of the output matching circuit is used as an output terminal of the variable-gain amplifier circuit; wherein the variable-load circuit is configured so that at least two of the three reactance function elements are capable of changing their reactance values; and wherein corresponding control terminals of the at least two reactance function elements exercise control to change a variable inductance value or a variable capacitance value thereof in a coordinated manner to obtain a predetermined load impedance.