An amplifier circuit to amplify a sequence of echoes and to generate a corresponding sequence of amplified signals. In an embodiment, the amplifier includes an operational amplifier, with variable input and feedback resistances such that the ratio of the two resistances can be controlled. A gain control block controls the ratio in a time dependent manner to obtain desired gain factors for each of the echoes. The gain factors can be pre-computed such that all the echoes are gained to the same level in case of an ultra-sound system.