Patent ID: 7567122

Claim:
A method of providing direct current (DC) gain control voltages that operate in opposing manner, the method comprising: receiving at a first difference amplifier coupled to a variable gain amplifier: a first reference voltage, the first reference voltage corresponding to a summation of a DC shifted voltage and an emitter common mode voltage (ECMV), the ECMV derived from the variable gain amplifier; a first control terminal voltage; and a second control terminal voltage, the first and second control terminal voltage derived from a differential control voltage; receiving at a second difference amplifier coupled to the variable gain amplifier a second reference voltage, the first control terminal voltage, and the second control terminal voltage, the second reference voltage corresponding to a summation of a DC shifted voltage and a collector common mode voltage (CCMV), the CCMV derived from the variable gain amplifier; at the first difference amplifier, adding the first reference voltage to the second control terminal voltage to provide a first sum, and subtracting from the first sum the first control terminal voltage to provide a first DC gain control voltage; at the second difference amplifier, adding the second reference voltage to the first control terminal voltage to provide a second sum, and subtracting from the second sum the second control terminal voltage to provide a second DC gain control voltage that operates in opposing manner to the first DC gain control voltage; and providing the first DC gain control voltage and the second DC gain control voltage to the variable gain amplifier.