An amplifier circuit and a method of signal amplification are provided. The amplifier circuit includes a first amplifier and a charge pump. The first amplifier includes a first terminal, a second terminal, and a third terminal. The first terminal is coupled to a first external voltage. The second terminal is coupled to a negative voltage. The third terminal is coupled to a ground reference voltage. The charge pump is coupled to the first amplifier for providing the negative voltage transformed from a second external voltage.