Patent ID: 7382175

Claim:
A frequency mixer comprising: a first MOS transistor, a local oscillator signal differential pair including a second MOS transistor and a third MOS transistor having substantially identical properties, a first load, a second load, and a control circuit, wherein said first MOS transistor receives an RE signal at a gate, said second MOS transistor has a source connected to a source of said third MOS transistor, and a connection node thereof is connected to a drain of said first MOS transistor, said second MOS transistor receives a local oscillator signal at a gate, and has a drain connected to said first load, said third MOS transistor receives an inverted local oscillator signal at a gate, and has a drain connected to said second load, said second MOS transistor outputs an IF signal from a drain, said third MOS transistor outputs an inverted IF signal from a drain, said first load and said second load are connected to a fixed potential, and said control circuit receives said RF signal and outputs a current to the drain of said first MOS transistor to decrease monotonously said current with respect to an amplitude of said RF signal, said control circuit comprises a fourth MOS transistor and a fifth MOS transistor having substantially identical properties, a sixth MOS transistor, a seventh MOS transistor, a first constant current source, a second constant current source, and a first capacitor, said fourth MOS transistor receives said RF input signal at a gate, and has a drain connected to the fixed potential, said fifth MOS transistor has a gate connected to the fixed potential, and a drain connected to said second constant current source, a drain and gate of said sixth MOS transistor, said first capacitor, a gate of said seventh MOS transistor, and said first capacitor, said fourth MOS transistor has a source connected to a source of said fifth MOS transistor, and a connection node thereof is connected to said first constant current source, said second constant current source, a source of said sixth MOS transistor, said first capacitor, and a source of said seventh MOS transistor are connected to the fixed potential, said seventh MOS transistor has a drain connected to the drain of said first MOS transistor, said second constant current source outputs a current lower than said first constant current source, and a drain current of said seventh MOS transistor is decreased monotonously with respect to the amplitude of said RF signal.