Neural signal front-end amplifier in 45 nm technology

In this paper, a front-end amplifier is designed in 45nm CMOS technology (previously designed in 180 nm technology) for recording neural signals. This amplifier consists of three stages -(1) a pre-amplifier with a feedback loop, (2) a current gain stage with adjustable gain, and (3) a tunable filter. The first stage is a current-mode pre-amplifier with feedback loop. The feedback loop is used to bypass dc-offset current generated at the electrode-tissue interface. Adjustable current-gain stage is the second stage which is used to adjust the gain of the amplifier by the application of digital signals. Tunable filter (third stage) adjusts the low-pass cut-off frequency for different neural signals. All the stages in the amplifier are current mode circuits. To convert the output current signal of the tunable filter into voltage signal a transimpedance amplifier is used. The measured maximum voltage gain of the amplifier is 72.5 db. The maximum current noise is 23pA/√Hz, and the power consumption is 6μw at 0.8V power supply.