Patent ID: 6803819
Filing Date: 2004-10-12
Classification: H03F,H03G

Abstract:
A variable gain amplifier comprising:(a) an amplification unit for amplifying input signals applied to first and second input terminals, differentially, and outputting the amplified signals to first and second output terminals, respectively; (b) first gain control unit having an input terminal, first and second output terminals, and first and second control terminals, wherein said first gain control unit controls currents flowing through the first and the second output terminals according to third + and âˆ’ control signals applied to the first and the second control terminals, respectively; (c) second gain control unit having an input terminal, first and second output terminals, and first and second control terminals, wherein said second gain control unit controls current flowing through the first and the second output terminals according to the third + and âˆ’ control signals applied to the first and the second control terminals, respectively; and (d) a degeneration impedance unit having first and second control terminals, and operably connected between the amplification unit and first voltage source, whose impedance value is controlled by first and second control signals, wherein the first and the second input terminals of said amplification unit form + and âˆ’ input terminals, respectively, and the first and the second output terminals of said amplification unit are connected to input terminals of said first and said second gain control units, respectively, and wherein the first output terminal of said first gain control unit is connected to the second output terminal of said second gain control unit, and forms âˆ’ output terminal, and the second output terminal of said first gain control unit is connected to the first output terminal of said second gain control unit, and forms + output terminal.