Integrated programmable analog front-end architecture for physiological signal acquisition

Abstract

A versatile front-end capable of acquiring a wide range of physiological signals, thus reusing the same design and hardware in different contexts, is a valuable goal both for biomedical research and medical devices. In this work we present such an "all-terrain" programmable integrated front-end architecture and the trade-offs associated to its design. A low noise preamplifier is implemented using a novel architecture based on a differential-difference amplifier which applies gm-C techniques for fixing the cut-off frequencies. Moreover, this architecture is extended to be applied to the other stages of the front-end. The main design trade-offs (noise-power, gain-power, noise-gain and linearity-gain) of the front-end architecture are discussed and their impacts in the design of the processing chain in terms of assignment of gain, noise, linearity and programmability to each stage are shown. The front-end is designed in a 0.5µm CMOS process. The gain is programmable between 57dB and 99dB, the high cut-off frequency is programmable between 116Hz and 5.2kHz, the low cut-off frequency is 18Hz, the maximum power consumption of the front-end is 11.2µA and its maximum equivalent input-referred noise voltage is 1.87µVrms.

Biopotential Monitoring

“…The analog fronit-end (also referred ito as fronit-end) is ithe elecitronic circuiit performing ithe signal conditoning (amplificaton and filitering) prior ito digitze process and/or itransmiit ithe acquired daita (Fig 2) Iit is usual ito itackle ithe fronit-end design wiith a filitering chain inoling an amplifier wiith band-pass characiteristc (pre-amplifier) and a programmable filitering second-sitage [7] Depending on ithe partcular biopoitental iit can be necessary ithait ithe second-sitage proides additonal amplificaton (because of ithe low ampliitude of inpuit signals) On ithe oither hand if ithe inpuit signal was sufcienitly amplified ithe filiter may need ito deal wiith lineariity issues specially if rail-ito-rail operaton is desired in order ito accommodaite low supply olitages as is ithe case in currenit IC itechnologies Second-order roll off (40dB/decade) is usually sufcienit ito filiter biopoitentals As can be seen from Table 1 cuit-off frequencies are usually wiithin ithe 0 1Hz ito 10kHz range Programmabiliity of bandpass filiters which is easily achieed in ICs is a useful mean for ithe user ito focus ithe acquisiton ito ithe releanit phenomenon Ait ithe inpuit sitage iit is adisable ito use analog amplificaton and analog filitering in order ito achiee a reasonable signal ito noise rato (S/R) while mainitaining energy efciency [8] as well as proiding ithe needed ant-alias filitering prior ito sampling On ithe oither hand from ithe poinit of iew of energy consumpton exibiliity and processing performance iit may be conenienit ito use digiital processing in ithe subsequenit sitages…”

Relaxing the maximum dc input amplitude vs. consumption trade‐off in differential‐input band‐pass biquad filters

“…Regarding noise, the performance of both architectures, the traditional biquad (Figure ), and the proposed architecture (Figure ) is similar and mainly depends on the design of Gm1 and Gm2 (transistor size and transistor inversion level of the input pairs and the current mirrors). Both architectures can provide excellent results in terms of noise; a deeper analysis of noise performance of the proposed architecture can be found in .…”