Patent ID: 6941118

Claim:
A negative feedback amplifier comprising: an input portion for receiving an input signal to said negative feedback amplifier; an adder unit coupled to said input portion; a quadrature modulator for performing a quadrature modulation on an output of said adder unit; a first signal level variable unit coupled to said quadrature modulator; an amplifier unit coupled to said first signal level variable unit; a feedback circuit for negative feedbacking an output of said amplifier unit to said adder unit, said feedback circuit including a first control unit for controlling a signal level of said amplifier unit; and a second control unit, coupled to said adder unit, for controlling an output of said first signal level variable unit so that said output of said adder unit becomes a predetermined output level, wherein said first control unit has a first detection circuit for detecting a first signal that represents said output level from said amplifier unit and a second signal level variable unit for adjusting the signal level of said feedback circuit based on said first signal, wherein said second control unit has a second detection circuit for detecting a second signal that represents an output level of said adder unit, and controls said output level of said first signal level variable unit based on said second signal, wherein said first and second control units detect said signal levels of said feedback circuit and said adder unit, and compare said signal levels of said feedback circuit and said adder unit, and wherein said first signal level variable unit is controlled based on a result of the comparison.