Hitachi-Kokusai Electric Inc.

Kokusai Electric Co., Ltd.

Hiromichi Hayase

Kotaro Takenaga

Takeshi Ishigami

An amplifier apparatus in which a signal is amplified by an amplifier and distortion produced by the amplifier is compensated for, that can continue to operate even in cases where the amplitude of a distortion component contained in the amplified signal after distortion compensation has become large. Distortion component amplitude detection meansanddetect the amplitude of distortion components produced by the amplifierthat are contained in signals amplified by the amplifierafter distortion compensation, and when the amplitude of a detected distortion component exceeds a predetermined threshold value, amplified signal level reduction control meansandperform control to reduce the level of the signal amplified by the amplifier. In the distortion compensation, the predistortion circuitgenerates distortion in respect of a signal that has not yet been amplified by the amplifier, and based on the detected amplitude of the distortion component, predistortion control meanscontrols the distortion produced by the predistortion circuit

Amplification device

A metal-oxide semiconductor field-effect transistor (MOSFET) amplifier circuit includes a compensation circuit with a low cost MOSFET and a constant current circuit providing a constant drain current of the MOSFET, which maintains an operational point of the amplifier at an optimal state at all times. The MOSFET amplifier circuit includes a first MOSFET, a constant current circuit including a variable resistor, an operational amplifier, a power supply and a resistor, a second MOSFET having a constant current generated by the constant current circuit as a drain current thereof, and a voltage control circuit including operational amplifiers and resistors for applying a gate source voltage of the second MOSFET to the first MOSFET as a gate-source voltage thereof.

Growing community of inventors

Tokyo, Japan

Hiromichi Hayase