This paper presents the design of a neurostimulator performing biphasic ultra-high-frequency electrical stimulation while being driven from ultrasound energy. Unlike conventional constant current or constant voltage stimulators or state-of-the-art ultra-high-frequency stimulators, the system does not convert the input AC signal into regulated DC for storing power and supplying the elements of the circuits. Instead, it uses the received ultrasonic signal frequency (≥1 MHz) for electrically stimulating the tissue directly, and it achieves biphasic stimulation with external control and without storing extra power. This results in a highly efficient and miniature circuit, which has the potential to be used in bioelectronic medicine for stimulating small peripheral nerves deep inside the body. The operation of the circuit was first simulated in LTSpice using a lumped elements model for the impedance of the piezoelectric receivers and the load. Finally, a prototype was tested in vitro with commercial transducers and platinum-iridium electrodes as load.