This paper presents a third-order single-loop delta-sigma modulator of a biomedical micro-system for portable electroencephalogram（EEG） monitoring applications.To reduce the power consumption,the loop filter of the proposed modulator is implemented by applying a switched-capacitor structure.The modulator is designed in a 0.35-μm 2P4M standard CMOS process,with an active area of 365×290μm^2.Experimental results show that this modulator achieves a 68 dB dynamic range with an input sinusoidal signal of 100 Hz signal bandwidth under a 64 over-sampling ratio.The whole circuit consumes 515μW under a 2.5 V power supply,which is suitable for portable EEG monitoring.
A fully-differential bandpass CMOS （complementary metal oxide semiconductor） preamplifier for extra- cellular neural recording is presented. The capacitive-coupled and capacitive-feedback topology is adopted. The preamplifier has a midband gain of 20.4 dB and a DC gain of 0. The -3 dB upper cut-off frequency of the preamplifier is 6.7 kHz. The lower cut-off frequency can be adjusted for amplifying the field or action potentials located in different bands. It has an input-referred noise of 8.2 μVrms integrated from 0.15 Hz to 6.7 kHz for recording the local field potentials and the mixed neural spikes with a power dissipation of 23.1μW from a 3.3 V supply. A bandgap reference circuitry is also designed for providing the biasing voltage and current. The 0.22 mm2 prototype chip, including the preamplifier and its biasing circuitry, is fabricated in the 0.35-μm N-well CMOS 2P4M process.
A single die 1.2 V multi-stage noise shaping（Mash） 2-2 delta sigma analog to digital converter（ADC）for wide applications is implemented. The configurable Mash 2-2 modulator with a new decimation filter design is presented to achieve wide and high dynamic range（DR） for multiple practical applications. The novel modulator can be configured as a Mash 2-2 modulator for high precision or a 2-order modulator for low DR. The decimation filter is designed to select the OSR flexibly among cascaded integrator comb（CIC） filter and two half-band filters（HBF）. The serial peripheral interface（SPI） can be used to adjust the sampling frequency and the oversampling ratio（OSR）. The design was fabricated in a 0.13 m CMOS process with an area of 0.91 mm2and a total power of 5.2 mW. The measurement results show that the dynamic range（DR） of the proposed ADC can change from 55to 95 dB with the configurable OSR from 16 to 256. The spurious free dynamic range（SFDR） and signal-to-noise distortion ratio（SNDR） can get 99 dB and 86.5 dB, respectively.
In this paper, a silicon-based neural probe with microfluidic channels was developed and evaluated. The probe can deliver chemicals or drugs to the target neurons while simultaneously recording the electrical action of these neurons extracellularly. The probe was fabricated by double-sided deep reactive ion etching （DRIE） from a silicon-on-insulator （SO1） wafer. The flu- idic channels were formed with V-shape groove etching on the silicon probe and sealed with silicon nitride and parylene-C. The shank of the probe is 4 mm long and 120 ~tm wide. The thickness of the probe is 100 ~tm. The probe has two fluidic chan- nels and two recording sites. The microfluidic channels can withstand a pressure drop as much as 30 kPa and the flow resisti ity of the microfluidic channel is 0.13 μL min-1 kPa-1, The typical impedance of the neural electrode is 32.3 kΩ at 1 kHz at room temperature.
GUO Kai PEI WeiHua LI XiaoQian GUI Qiang TANG RongYu LIU Jian CHEN HongDa
