VARIABLE GAIN AMPLIFIER, AUTOMATIC GAIN CONTROL AMPLIFIER, AUTOMATIC GAIN CONTROL SYSTEM, AND RADIO RECEIVER

摘要

PROBLEM TO BE SOLVED: To obtain an improved variable gain amplifier by continuously varying the performance of the amplifier between low-gain high linearity and high-gain low linearity and varying DC biases to the base of multiple transistor(TR) amplifiers. SOLUTION: The DC bias to a TR Q2 is controlled by a grounded low-current source I1. The DC bias for a TR Q1 is provided by a resistor R1 coupled between the base and collector of the TR Q1. The DC bias for the TR Q2 is provided by a resistor R2 coupled between the collector of the TR Q1 and the base of the TR Q2. This constitution essentially reflects a DC current flowing through the collector-emitter path of the TR Q2 on the current provided by a current generator I1. The DC bias for a TR Q6 is the same.