Nec Corporation

Norio Terada

Kazuo Tokuda

A variable gain amplifier has a first amplifier circuit whose gain is A/n times (A being a real number excepting '0', and n being a real number larger than 1); a second amplifier circuit whose gain is A(n-1/n) times; level converter for level converting an output signal from the second amplifier circuit at a ratio corresponding to a level of a gain control signal having a predetermined level controllable range and at a ratio of 1/(n+1) at a central level within the level controllable range of the gain control signal; and an adder circuit for adding together an output signal from the level converter and an output signal from the first amplifier circuit at the ratio of 1:1. The variable gain amplifier has a gain controllable range of among 1/n.about.1.about.n times as the level of the gain control signal changes among the minimum level.about.the central level.about.the maximum level. When the gain of the second amplifier circuit is set to A(m-1/n) times (m being a real number larger than 1) and a level conversion ratio of the level converter is set to (1-1/n)/(m-1/n) at the central level of the gain control signal, the variable gain amplifer having the gain controllable range of among A/n.about.A.about.mA times is realized.

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Kanagawa, Japan

Norio Terada