2020 Volume 17 Issue 17 Pages 20200238
Negative impedance convertor is introduced to build a high input impedance chopper IA for implantable EEG recording. The compensation theory is analyzed in detail to reveal the characteristics of the impedance boosting method. The proposed chopper IA achieves very high input impedance of 18.9 GΩ and 18.5 GΩ at DC and 100 Hz respectively. It can reach 5.8 GΩ even at 1 kHz. With the common-mode feedback loop, up to 600 mVpp common-mode interference tolerance and 97 dB CMRR are achieved. The amplifier is implemented in a 0.18µm standard CMOS process and takes a power consumption of 1.34 µW with a 1.2 V supply. The mid-band input referred noise PSD is 130 nV/sqrt(Hz) and an NEF of 4.89 is obtained.
