Sanyo Electric Co., Ltd.

Renesas Technology Corp.

Akira Hyogo

Keitaro Sekine

Hiroshi Komurasaki

Hisayasu Satoh

Masahiro Umewaka

Hiroya Yamamoto

Keiji Morijiri

Kinya Hosoda

A tuning circuit having an amplitude-varying function is disclosed that comprises a coil, a capacitor, and a resistance-adjusting element connected in parallel to the coil and the capacitor for varying resistance at time of resonance of the tuning circuit, wherein the amplitude of an output signal of the tuning circuit is varied by varying the resistance with the resistance-adjusting element.

Tuning circuit having amplitude-varying function

A variable gain amplifier is configured of an amplification circuit and a control circuit controlling a gain of the amplification circuit. The amplification circuit has first and second MOS transistors identical in characteristics and having respective sources connected to a first fixed potential. The amplification circuit has a differential gain proportional to a square root of a ratio between a current flowing through the first MOS transistor and a current flowing through the second MOS transistor. The control circuit applies a potential corresponding to a constant voltage plus a control voltage to a gate of the first MOS transistor and a potential corresponding to the constant voltage minus the control voltage to a gate of the second MOS transistor.

Variable gain amplifier with a gain exhibiting a linear in dB characteristic relative to a control voltage

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Chiba, Japan

Akira Hyogo