HBT MONOLITHIC VARIABLE GAIN AMPLIFICATION CIRCUIT WITH BIAS COMPENSATION AND BUFFERING METHOD

摘要

PURPOSE: To obtain high performance efficiently over a wide operation range by allowing a series feedback path to have a PIN diode which operates as a variable resistance element and receives a variable gain control signal so as to generate a variable gain. CONSTITUTION: An input voltage VIN is applied to an input terminal 12 and transmitted to the base 14 of a transistor TRQ1. The amplification gain generated by the TRQ1 is controlled with a variable control signal shown by a variable gain control voltage VGC. This variable gain control voltage VGC is generated by an electronic control unit. The variable gain control voltage VGC is transmitted through a resistance RPD and PIN diodes PD1 and PD2. Then the PIN diode PD1 operates so as to supply variable resistance according to a current IC flowing through it and effectively vary the amplifying circuit gain. The PIN diode PD2, on the other hand, effectively supplies a mirror current operating as a bias to the diode PD1.