According to one embodiment of the present invention, there is a high frequency circuit having a multi-chip module structure, including a semiconductor substrate set formed with discrete transistors connected in series, a first dielectric substrate set formed with capacitors, and a second dielectric substrate set formed with strip lines.

A semiconductor power device comprises a flange, a die having a gate, a source, and a drain. The source is electrically coupled to the flange. A drain matching circuit is located on the flange having an input, an output and a bias input, the input being coupled with the drain. The drain matching circuit comprises an inductor coupled in series with a first capacitor between the drain and flange and a second capacitor arranged next to the first capacitor, wherein the second capacitor is coupled with the bias input and in parallel with the first capacitor through a second inductor. An input terminal is mechanically coupled to the flange and electrically coupled with the gate, an output terminal is mechanically coupled to the flange and electrically coupled with the output of the drain matching circuit, and an input bias terminal is mechanically coupled to the flange and electrically coupled with the drain through the bias input.

A multi-stage, variable gain amplifier whose linearity is relatively insensitive to variations in gain control is disclosed. The amplifier includes a primary cascoded pair of transistors for producing a primary output current from an input voltage as a function of a primary cascode control voltage. The amplifier further includes one or more secondary cascoded pairs of transistors coupled to the primary cascoded pair of transistors for producing one or more secondary output currents from the input voltage as a function of one or more secondary cascode control voltages. The output current of the RF circuit is a sum of the primary output current and the one or more secondary output currents

An amplifier circuit improved in linearity and frequency band comprises an amplification block, a feedback block and an output block. The amplification block comprises a main transistor, an auxiliary transistor, a first capacitor, a second capacitor, a main transistor bias unit, and an auxiliary transistor bias unit. The main transistor bias unit comprises a first bias resistor. The auxiliary transistor bias unit comprises a second bias resistor. The feedback block comprises first and second feedback resistors, and the output block comprises an output resistor and an output transistor.

An amplifier circuit improved in linearity and frequency band comprises an amplification block, a feedback block and an output block. The amplification block comprises a main transistor, an auxiliary transistor, a first capacitor, a second capacitor, a main transistor bias unit, and an auxiliary transistor bias unit. The main transistor bias unit comprises a first bias resistor. The auxiliary transistor bias unit comprises a second bias resistor. The feedback block comprises first and second feedback resistors, and the output block comprises an output resistor and an output transistor.

The object of the present invention is to provide a bipolar transistor which is excellent in uniformity of current distribution in spite of a small ballast resistance, and can constitute an amplifier showing high efficiency and low distortion with little deterioration of distortion even when a digital modulation wave is input thereto. A high frequency power amplifier of the present invention comprises a plurality of transistor blocks having a bipolar transistor, wherein each of the transistor blocks includes a resistance connected to an emitter of the bipolar transistor, a reference voltage generation circuit for generating a reference voltage as a base bias of the bipolar transistor, and a bias generation circuit connected to a base of the bipolar transistor, the bias generation circuit generating a base bias voltage by converting the reference voltage.