Reconfigurable Low-noise Multichannel Amplifier for Neurochemical Recording

摘要

An integrated circuit for real-time, simultaneous recording of electrical and chemical(pH) signatures of neural activity is presented. It consists of six recording channels, three for electrical and three for chemical signals. Each channel has a low-noise amplifier which utilizes a new and optimized technique of flicker noise suppression. Our approach is based on a modified switched bias current technique. Both electrical and chemical amplifiers use the same circuit topology and have a common footprint, but the type of amplifier is reconfigured by controlling the bias current, which controls the bandwidth of the amplifier. The chip was fabricated using an AMS 0.35μm and four metal double poly CMOS technology. Measured noise reduction depends on the switching frequency. Bench tests have shown that our technique achieves up to 60% intrinsic 1/f noise suppression by determining an optimal switching frequency, without additional circuit complexity or an increase in transistor and chip area. The amplifier was designed to exhibit a 60 dB closed loop gain for electrical neural signals, and a 20 dB closed loop gain neurochemical signals. Each channel within the design occupied an area of 3.66mm^{2. This circuit design will be used as an integrated circuit for a real-time bimodal recording of neural activity for closed-loop neuromodulation therapies.}