Abstract: To obtain a more stable gain control range and to reduce power consumption with a smaller scale circuitry having simpler configuration for gain control, a high frequency variable gain amplifier includes multi stage transistor amplifiers, a change-over switch circuit for controlling supplying and interruption of a power supply voltage, and a field effect transistor switch circuit with grounded-gate connection inserted in a bypass path midway across an input terminal and an output terminal. The source of this field effect transistor switch is in direct current-connection to the drain of a field effect transistor of the final stage transistor amplifier circuit. When a power supply voltage is supplied to each of the transistor amplifiers via the change-over switch circuit, the field effect transistor switch is turned "off" and when the power supply voltage is interrupted, the field effect transistor switch is tuned "on".

Abstract: A radio frequency amplifier, for amplifying a radio frequency signal, comprises a plurality of active element groups, each comprising one or more active elements for amplifying a signal, with input terminals of said one or more active elements being combined to form a single input terminal and output terminals of said one or more active elements being combined to form a single output terminal and bias control means for controlling bias conditions of said plurality of active element groups arranged in such a manner that at low power output deterioration of the gain and distortion characteristics of the amplifier is avoided and sufficiently low power consumption can be achieved by switching the bias voltages of each of the active element groups of the high-frequency amplifier individually between an operating voltage and an off voltage.

Abstract: A high-frequency circuit package including a conductive substrate, and upper and lower shielding cases which come tightly into contact with opposite surfaces of the conductive substrate to define therein upper and lower shielding chambers. High-frequency circuits are mounted on the surfaces of the conductive substrate within the upper and lower chambers, respectively.