Development of a Neuromodulation System with Micro-LED Drive: Reducing Channel Mismatch and Enhancing Input Impedance

This paper introduces an optogenetic neuromodulation system consisting of a neural signal acquisition module, a three-channel optogenetic stimulation module, and a three-channel micro-LED monitoring module. The micro-LED driver module facilitates continuous, real-time tracking of the micro-LEDs’ long-term performance, offering direct feedback on their operational status for user convenience. The neural signal acquisition module employs a GCIA (Group-Chopping Instrumentation Amplifier) structure to achieve multi-channel gating, minimizing inter-channel mismatch. Multi-stage chopping reduces the equivalent input impedance, with the first stage utilizing a DDA (Differential Difference Amplifier) structure to enhance input impedance. The amplifier employs an open-loop structure to improve area efficiency and utilizes switched-capacitor filters for signal filtering. Fabricated using the TSMC 65nm process, the improved GCIA achieves a gain of 43 dB, a bandwidth of 0.5–5 kHz, and an inter-channel mismatch of less than 0.0428%. The equivalent input-referred noise is 3.3 µVrm, the input impedance reaches 535 MΩ, and the static power consumption is 1.05 µW.