Gain equalizer and method for controlling tunable gain of gain equalizer

A method for controlling a tunable gain of a gain equalizer, comprising:

• utilizing a first common source stage of the gain equalizer to receive an input signal via gate terminals of a first input transistor and a second input transistor within the first common source stage, respectively;
• utilizing the first common source stage to apply the tunable gain to the input signal for generating the amplified signal on drain terminals of a first cascode transistor and a second cascode transistor within the first common source stage, respectively, wherein the first cascode transistor and the second cascode transistor are respectively coupled to the first input transistor and the second input transistor;
• utilizing a first switch array of the gain equalizer to control the tunable gain according to an equivalent impedance of the first switch array, wherein the first switch array is coupled between respective source terminals of the first cascode transistor and the second cascode transistor;
• receiving the input signal via gate terminals of a third input transistor and a fourth input transistor within a second common source stage, respectively, wherein a third cascode transistor within the second common source stage is coupled between the third input transistor and the drain terminal of the first cascode transistor, and a fourth cascode transistor within the second common source stage is coupled between the fourth input transistor and the drain terminal of the second cascode transistor;
• and
• utilizing a second switch array of the gain equalizer to further control the tunable gain according to an equivalent impedance of the second switch array, wherein the second switch array is coupled between respective source terminals of the third cascode transistor and the fourth cascode transistor, wherein the tunable gain is further controlled according to an equivalent impedance of the second switch array.