A Wide Input Range, Low-noise Neural Recording Amplifier IC With Adaptive Gain Control and Common-mode Cancellation Loop

This paper proposes a wide input range, low-noise neural recording amplifier IC with adaptive gain control and a feedback-based common-mode cancellation loop (CMCL) for bidirectional neuromodulation applications. The proposed amplifier operates with maximum gain and excellent noise performance under normal conditions, while automatically reducing its gain to extend the dynamic range (DR) and activating the CMCL in response to differential-mode (DM) and common-mode (CM) stimulation artifacts, respectively, thereby adjusting the DM gain to prevent amplifier saturation and removing the CM component. The total harmonic distortion (THD) of the circuit output is 0.822% with a 77 mV_PP DM input at a gain of 17.72 dB and 0.418% in the presence of a 1 V_PP CM artifact. Under ideal conditions, the amplifier maintains a gain of 40 dB with an input-referred noise (IRN) performance of 2.32 µV_rms over a bandwidth of 1 Hz to 10 kHz. The CMCL dynamically toggles on or off depending on the presence of artifacts to balance noise performance and artifact tolerance. The proposed amplifier is designed using 180 nm CMOS process, consumes 2 µW at 1-V supply, and occupies 0.36 mm² of die area.