The present invention provides an amplifier circuit, wherein the amplifier circuit includes an operational amplifier and a feedback path. The operational amplifier has an input terminal and an output terminal, and is arranged for receiving an input signal to generate an output signal. The feedback path is coupled between the input terminal and the output terminal of the operational amplifier, wherein the feedback path comprises at least two poly resistors, and a depletion region of at least one of the two poly resistors is biased by the output signal generated by the operational amplifier.