Abstract: Disclosed a power amplifier including a main amplifier with class bias AB and a peak amplifier with class C bias. A quarter-wave length transmission line having a length equal to one-fourth of the wave-length of a fundamental frequency is connected to an output side of the peak amplifier. Outputs of the main amplifier and the peak amplifier are combined. An envelope amplifier that modulates the drain bias voltage in accordance with an envelope of the modulation wave input signal and an envelope detector are provided as a drain-bias circuit for the main amplifier (FIG. 1).

Abstract: A micro-wave power amplifier which amplifies a micro-wave signal including a plurality of carrier frequencies different from one another, includes (a) a field effect transistor having a grounded source, (b) a first difference frequency circuit which is electrically connected to a drain of the field effect transistor, and is short-circuited at a difference frequency between the carrier frequencies, and (c) a second difference frequency circuit which is electrically connected to a gate of the field effect transistor, and is short-circuited at a difference frequency between the carrier frequencies.

Abstract: A 180° phase shift circuit includes a balun having an unbalanced port and a pair of balanced ports, a pair of impedance matching lines each connected between one of the pair of balanced ports and one of a pair of balanced signal terminals, and a &lgr;g/2 distributed parameter line having ends each connected via a resistor to a node connecting together corresponding impedance matching line and corresponding balanced signal terminal.

Abstract: A micro-wave power amplifier which amplifies a micro-wave signal including a plurality of carrier frequencies different from one another, includes (a) a field effect transistor having a grounded source, (b) a first difference frequency circuit which is electrically connected to a drain of the field effect transistor, and is short-circuited at a difference frequency between the carrier frequencies, and (c) a second difference frequency circuit which is electrically connected to a gate of the field effect transistor, and is short-circuited at a difference frequency between the carrier frequencies.

Abstract: A microwave amplifier includes an amplifying device having a first contact region extending in a width direction, an output side impedance device spaced from the amplifying device in a transmission direction perpendicular to the width direction, the impedance device having a second contact region connected to the first contact region of the amplifying device, the second contact region extending in the width direction, and a smoothing circuit connected to one of the first and second contact regions for smoothing a distortion in a microwave signal to be amplified by the amplifying device.

Abstract: A 180-degree phase shifter has two sets of transmission signal lines connected to one another and respectively coupled with an unbalanced signal transmission path connected to an input unbalanced signal terminal and a balanced signal transmission path connected output balanced signal terminals so that a designer can independently optimize the position of the input unbalanced signal terminal and the positions of the output balanced signal terminals.