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Versatile Bio-Processing Integrated Microsystem

This project involves the design and implementation of a bio-processing microsystem. Specifically, we are exploiting the weak, strong and moderate inversions behaviors of CMOS transistors to engineer robust, versatile and flexible processing systems for major bio-electrical systems. These signals include the electroencephalogram (EEG) from brain, the electrooculography (EOG) from eye, electrocardiography (ECG) from heart, electromyography (EMG) from muscle, and neural recordings. The neural recordings category includes intracranial EEG, neural spikes and local field potentials (LFPs).

A key challenge in this work is developing a monolithic integrated circuit without off-chip capacitors or off-chip resistors while operating at low noise and power. That means the noise efficiency factor (NEF) should tend towards the theoretical BJT NEF of 1. Also, the chip should work in the low mH range with bandwidth that can extend to the kH range.

Furthermore, the chip should also manage the offsets which are usually inherent in these signals arising from the electrode-tissue interface. Above all, the total thermal and flicker noise of the chip must be lower that the minimal noise from the bio-signals (always in uVrms range). To ensure the tissues are not destroyed during data acquisition and processing, the total power should not exceed 1mW. This is necessary as next generation neural recording is expected to use thousands of electrodes. Designing amplifiers in nanoWatt range remains one of the main ways of supporting that advancement.

A low power, low noise delta sigma ADC for quantizing the signal is incorporated to the chip front end. In designing the decimation filter for the ADC, we use counters to count the pulse density modulated signal under the supervision of another counter. Finally, an SPI is used to interface it to PC or other processing machines.

[Full details would be available after the publication of the chip]


Students: N. Ekekwe, E. Choi, T. Murray, N. Silva
Advisers: A. Andreou, R. Etienne-Cummings, P. Pouliquen