Apparatus, systems, and methods for current monitoring in ultrasound powered neurostimulation. The apparatus may include an ultrasound transmitter configured to emit an ultrasound output directed at a piezoelectric device implanted in biological tissue. The apparatus may also include a detector configured to detect an induced current in response to the ultrasound output in the biological tissue. The piezoelectric device may include a piezoelectric material and a diode. The apparatus may include a feedback mechanism to control the amount of induced current in the biological tissue.
