Acoustic metamaterials have sub-wavelength band gaps，which can be applied to noise and vibration control. With the introduction of piezoelectric materials and resonant shunts，tunable locally resonant band gaps can be achieved by utilizing their electromechanical coupling and electromagnetic oscillation. However，restricted by the limited electromechanical coupling coefficients of available piezoelectric materials，the band width of traditional piezoelectric acoustic metamaterials is generally narrow，which is barely to satisfy the requirement of low-frequency and broad band gaps in noise and vibration of flexible structures. Consequently，this paper proposes a type of piezoelectric acoustic metamaterials with amplified resonant shunts. Piezoelectric patches are partitioned into sensing poles and driving poles. The output voltage of the sensing pole is amplified by an operational amplifier circuit. The amplified voltage is applied on a resonant shunt to enhance the local resonance and broaden the band width. Finite element method is adopted to build the mathematical model and evaluate the band gaps. Also，the variations of band location and width with amplification coefficient are analyzed，including the relation between equivalent modulus and band gaps. The commercial finite element software is employed to analyze the vibrational transmission of the finite periods beam and validate the calculation method of band gaps. The investigation results demonstrate that the locally resonant effect can be effectively enhanced by amplification circuits. The band frequency decreases with the increasing of amplification coefficient，whereas the band width increases accordingly. Hence，this work is of great importance in design of low frequency and broad band piezoelectric acoustic metamaterials.