A 1-V 4.6-μW/channel Fully Differential Neural Recording Front-end IC with Current-controlled Pseudoresistor in 0.18-μm CMOS

Abstract

This paper presents a fully differential implantable neural recording front-end IC for monitoring neural activities. Each analog front-end (AFE) consists of a low-noise amplifier (LNA), a variable gain amplifier (VGA), and a buffer. The output signal of the AFE is digitized through a successive approximation register analog-to-digital converter (SAR ADC). The LNA adopts the currentreuse technique to improve the current efficiency, achieving the power consumption as low as 0.95 μW. The implemented LNA has the gain of 40 dB, the lowpass cutoff frequency of 10 kHz, and the high-pass cutoff frequency of sub-1 Hz which is realized using the current-controlled pseudoresistor. The VGA controls the gain from 21.9 dB to 33.9 dB for efficient digitization while consuming the power of 0.35 μW. The buffer drives the capacitive DAC of the ADC and consumes the power of 3.28 μW. The fabricated AFE occupies the area of 0.11 ㎟/Channel and consumes 4.6 μW/Channel under 1-V supply voltage. Each channel achieves the input-referred noise of 2.88 μVSUBrms/SUB, the NEF of 2.38, and the NEF²VSUBDD/SUB of 5.67. The front-end IC is implemented in a standard 1P6M 0.18-mm CMOS process.