A Self-Compensated, Low-Offset Voltage Buffer for Input Impedance Boosting in Chopped Neural Front-Ends

Modern neuromodulation systems feature parallel low-noise recording on a large number of channels, limiting the available area per channel. This has made chopper-stabilization the modality of choice for many recently published implementations. To tackle the issue of decreased input impedance, the auxiliary path boosting scheme can be used, which minimizes the amount of charge drawn from the electrode by precharging the input capacitors through a voltage buffer. However, the offset of the buffer translates to a deterministic amount of charge per time that is transfered to the electrodes and accelerates electrode aging. If blocking capacitors are used as a safety feature, the offset-induced charge can lead to a voltage drift due to charge accumulation, that slowly saturates the buffers. This paper presents a voltage buffer that uses a self-compensation scheme to reduce the time-averaged offset to sub − 20 μV, thereby minimizing excess charge.