Design an‎d development an implantable neural stimulator

9/9/2026 12:00:00 AM

In this thesis, a neural stimulation system has been designed an‎d implemented. The system consists of four main parts: a rectifier, a voltage regulator, a charge pump, an‎d a current-mode neural stimulator. The voltage regulator requires a suitable reference voltage. Furthermore, the stimulator needs a controller to manage its stimulation phases. Therefore, in addition to the main blocks mentioned above, these two sections have also been designed. In designing the rectifier, important characteristics such as high efficiency an‎d low voltage dro‎p were considered. For this part, an active diode structure with cross-coupled gates was used. The main idea of this circuit is to employ a clamp structure after the cross-coupled stage to increase the voltage level an‎d reduce the output voltage dro‎p relative to the input. According to the results, the rectifier circuit achieves a maximum voltage conversion ratio an‎d power conversion efficiency of 128 an‎d 86.86%, respectively. In the voltage regulator section, a ban‎dgap reference circuit is used as a precise reference voltage. The ban‎dgap circuit design combines two PTAT an‎d CTAT voltage generator circuits with another circuit using transistors in the saturation region. This combination enables the design of a reference that is resistant to variations in temperature, fabrication process, an‎d supply voltage. The output results show the circuit is highly stable against supply voltage an‎d temperature changes, with a line sensitivity an‎d temperature coefficient of 0.61 %/V an‎d 18.06 ppm/°C, respectively. A Self-cascode structure was used for designing the charge pump. Utilizing this structure significantly reduces the circuitʹs power consumption an‎d increases its stability against clock signal rise an‎d fall time variations. A new structure was used in the neural stimulator design to achieve charge balancing. In this current-mode stimulator, a reference current is first generated by the reference circuit an‎d fed into a current gain control block. This current then enters a 5-bit current-mode digital-to-analog converter (DAC) to achieve considerable accuracy for the stimulation current. The current is then passed through a high-impedance current mirror to ensure a acceptable level of charge balance between the anodic an‎d cathodic phases. Finally, a high-voltage driver, designed as an H-bridge, will deliver the stimulation current to the body tissue via the electrodes. All designs in this project were implemented in a 180 nm CMOS technology (3.3V). The supply voltage for the neural stimulator was set to approximately four times the technologyʹs voltage (11.2V). Given the technology used, the output of the current gain control circuit, after passing through the current-mode DAC, is such that after amplification it can reach up to 3.2 mA. Consequently, it can be used for controlling epilepsy, muscle control, an‎d Parkinsonʹs disease, respectively. The measured voltage across the tissue during stimulation can reach up to 10.2V. In the stimulator circuit, there is very good matching between the anodic an‎d cathodic phases, an‎d due to the proposed structure, the charge mismatch is about 0.21%. Furthermore, to validate the stimulatorʹs functionality, animal testing was conducted to observe leg movement an‎d record the corresponding signal; the results are presented in the thesis.

يكسوساز , تثبيت‌كننده ولتاژ , تقويت‌كننده خطا , تحريك‌كننده عصبي , مبدل ديجيتال به آنالوگ , پمپ‌كننده بار , مرجع جريان

Current Reference , Charge Pump , DAC , Stimulator , Error Amplifier , Regulator , Rectifier

Mostafa Katebi

Abbas Erfanian omidvar