Low Power Instrumentation Amplifier for a Fully Implantable Neural Recording System

Recording neural signal from a living human body is a complex task and it is an important research issues for neuroscientists and researchers in biomedical engineering. The major issue to over- come in the design of a system that is aimed at being implant into the human body is having a low power consumption, low noise circuit and small dimension to minimize tissue damage. In this paper, specific issues of the most important part of such a neural acquisition system are presented; in particular, the design of a low-power amplifier, for a fully implantable neural recording system, is described. The amplifier uses a differential pair as input stage. Given that neural amplifiers must include differen- tial input pair to achieve a high common-mode ratio rejection (CMRR). The amplifier has been designed in the AMS 0.35 μm standard CMOS process. The amplifier current consumption is 4.61 μA at ±1V supply, which gives a power consumption of 9.22 μW. The low cutoff frequency is adjustable from 21 Hz to 100 Hz, with four tunable gains of 43.6 dB, 48 dB, 50 dB and 52.8 dB. The upper cutoff frequency is about 7.6 kHz. The CMRR is 113 dB and the power supply ratio rejection is PSRR > 73dB. The input referred noise is 14.8 μV rms over 100 10 kHz. The amplifier gives an input DC offset of 196 μV.