An amplifier is provided. The amplifier includes a pair of first input transistors, a first load, and a first canceling circuit. The pair of first input transistors is coupled between a pair of first differential nodes and a reference voltage source, for receiving a pair of input signals. The first load is coupled to the pair of first differential nodes and a pair of differential output terminals of the amplifier. The first canceling circuit is coupled between the first differential nodes. The canceling circuit is capable of balancing voltages, respectively, at the first differential nodes when the amplifier is turned off.