Since the use of pseudo-resistors became popular in of bio-amplifiers research, several works have been published, but a lack of knowledge about accurate experimental characterisation and simulation of these non-linear devices remains. An innovative experimental procedure concerning the characterisation of pseudo-resistors is presented. The proposed experimental procedure proves the existence of a linear operation region, where the device can operate like a very high resistance, which is mainly applied on bio-amplifier designs. The main experimental results of the electrical characterisation of pseudo-resistors are described in detail and compared with the SPICE results. The pseudo-resistor experimental curve response including the non-linear operation region is presented. Finally, a new non-linear polynomial resistor model to use in SPICE simulator, replacing with success the electrical representation model based on transistors models is proposed. The presented simulations were performed with Mentor Graphics Eldo TM SPICE simulator, using BSIM3V3.1 and PSP103.1 models. The MOSIS Educational Program fabricated the samples used in this work.
Professor Doutor do Programa de Pós-graduação em Administração da Universidade do Vale do Itajaí
RESUMOConsiderando o crescimento da representatividade de pequenos trabalhadores autônomos informais na economia brasileira e a consequente preocupação no desenvolvimento de políticas públicas que incentivem a formalização de negócios iniciantes, o presente estudo, de caráter descritivo, apresenta o perfil do microempreendedor individual catarinense e o compara aos dados nacionais. Para tal, utilizou-se a base de dados secundários disponibilizada no Portal do Empreendedor, site criado pelo governo para realização dos registros dos empresários. O estudo aponta as atividades mais comumente exercidas pelos empreendedores, bem como faixa etária, gênero e forma de atuação dessa população. A pesquisa também mostra a evolução no crescimento do número de microempreendedores individuais no estado, comparando-os ao número de empresas constituídas em outras modalidades. Conclui-se que o trabalhador autônomo informal identificou na Lei do Microempreendedor Individual uma alternativa adequada para regularizar suas atividades empresariais, ingressando na economia formal. Recebido em 07/08/14. Aprovado em 26/10/14. Avaliado pelo sistema double blind peer review. Publicado conforme normas da ABNT.
Palavras
This work presents a new fast model, based on piecewise linear (PWL) methodology, for pseudo-resistors SPICE simulation, including the non-linear working range, fully supported by experimental data. SPICE simulations with fixed resistances or transistor modelled as pseudoresistors do not reproduce simultaneously its real behavior for both the linear and the non-linear regions. A complete set of steps which validate the PWL macromodel for bio-amplifiers project is presented. As a case study, this paper addresses the pseudo-resistor characteristics operating in the non-linear region when implemented in a low-frequency bio-potential amplifier with narrow bandwidth, for use in heart rate meters and QRS complex monitoring systems. The use of the pseudo-resistor in this low-voltage low-power topology associates DC offset cancellation with an adequate frequency response. Moreover, this work shows that the non-linear characteristics of these devices can be used for a significant reduction in bio-amplifier recovery time (a.k.a. settling time) without any additional device or mechanism, making the heart rate measurements steadier and more reliable than obtained so far in current systems. The transient recovery time, as well as the response to QRS complex, was widely evaluated through experimental measurements and SPICE simulations, thanks to the proposed model. The bio-potential amplifier design was implemented using GF 8HP 0.13 μm BiCMOS technology from Global Foundries. Keywords: piecewise linear macro-model, MOS bipolar pseudo-resistor, pseudo-resistor, small recovery time, bio-potential amplifier, low power design
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