Compact chopper-stabilized neural amplifier with low-distortion high-pass filter in 0.13µm CMOS

A compact and low-distortion neural recording amplifier is presented. The amplifier consists of two stages of amplification using capacitive feedback to set a gain of 54dB. To minimize flicker noise in the 1st stage, internal chopping is utilized at the folded node of the OTA, resulting in flicker noise contribution from the input differential pair only. A low-distortion constant-VGS feedback circuit to set a low frequency high-pass pole is introduced. It is less sensitive to the output swing than the conventional sub-threshold MOS circuit. The amplifier fabricated in a standard 1.2V 0.13µm CMOS technology occupies 125×175µm² and achieves an NEF of 4.4, an input-referred noise of 4.7µV over a 5kHz bandwidth, a CMRR of 75dB and a THD of −50dB for a 0.6V output swing.