A Direct Digitizing Chopped Neural Recorder Using a Body-Induced Offset Based DC Servo Loop

This article presents a direct digitizing neural recorder that uses a body-induced offset based DC servo loop to cancel electrode offset (EDO) on-chip. The bulk of the input pair is used to create an offset, counteracting the EDO. The architecture does not require AC coupling capacitors which enables the use of chopping without impedance boosting while maintaining a large input impedance of 238 M$\Omega$ over the whole 10 kHz bandwidth. Implemented in a 180 nm HV-CMOS process, the prototype occupies a silicon area of only 0.02 mm² while consuming 12.8 μW and achieving 1.82 μV$_{\text{rms}}$ of input-referred noise in the local field potential (LFP) band and a NEF of 5.75.