Wireless integrated circuit for the acquisition of electrocorticogram signals

We present the design and characterization of amplifiers and control logic for an integrated circuit designed to record electrocorticograms (ECoG) from the surface of the brain. The chip, which was fabricated in a 0.6-μm BiCMOS process, contains 100 amplifiers, control logic, and circuits for wireless power and transmission of data. ECoG signals, sensed by electrodes, are capacitively coupled to the amplifiers. Each amplifier has a gain of 59.2 dB, a maximum bandwidth of 240 Hz, an input referred noise of 2.8μV, and consumes 4.5μW of power. The output of each amplifier is connected to a 10-bit ADC via an adaptive-bias buffer and transmission gate whose transparency is set by the control logic. The control logic time-shares the ADC by multiplexing through one of five preset patterns of 32 on-chip signals. The digitized waveforms are then broadcasted wirelessly using a 900 MHz FSK transmitter. The entire chip consumes 7.2 mW of power during operation.