An amplifier amplifying an input signal and the method thereof. The amplifier comprises first and second transconductor circuits. The first transconductor circuit, coupled to the first transistor, receives the first noise voltage to generate a first noise current. The second transconductor circuit, coupled in parallel to the first transconductor circuit, receives the second noise voltage to generate a second noise current such that the first and second noise currents cancel each other out to reduce a noise component in the output current when summing up together, and the first and second transconductor circuits are operated in a current mode.