Gain equalizer and method for controlling tunable gain of gain equalizer

Abstract

A gain equalizer and a method for controlling a tunable gain of the gain equalizer are provided. The gain equalizer includes a common source stage and a switch array. The common source stage is configured to apply the tunable gain to an input signal, in order to generate an amplified signal. The common source stage includes input transistors and cascode transistors, wherein the cascode transistors are respectively coupled to the input transistors. The input transistors are configured to receive the input signal via gate terminals of the input transistors, respectively, and the cascode transistors are configured to output the amplified signal via drain terminals of the cascode transistors, respectively. In addition, the switch array is coupled between respective source terminals of the cascode transistors, wherein the tunable gain is controlled according to an equivalent impedance of the switch array.