This thesis presents the design and development of two switching amplifiers used to drive the so-called smart material actuators. Different from conventional circuits, a smart material actuator is ordinarily a highly capacitive load. Its capacitance is non-linear and its strain is hysteretic with respect to its electrical control signal. This actuator's reactive load property usually causes a large portion of reactive power circulating between the power amplifier and the driven actuator, thus reduces the circuit efficiency in a linear power amplifier scenario. In this thesis, a switching amplifier design based on the PWM technique is proposed to develop a highly efficient power amplifier, and peak current mode control is proposed to reduce the actuator's hysteretic behavior. Since the low frequency current loop gain tends to be low due to the circuit's capacitive load, average current mode control is further proposed to boost the low frequency current loop gain and improve the amplifier's low frequency performance. Both of the circuits have been verified by prototype design and their experimental measurement results are given.