Modeling and experimental evaluation of pseudo-resistor’s temperature dependence

Abstract

This work presents the experimental temperature dependence evaluation of the pseudo-resistor piecewise linear (PWL) macromodel, for temperature ranging from 300 to 333 K. The studied macromodel is based on the PWL methodology and it can be used for pseudo-resistors SPICE simulation, including both linear and non-linear operation regions. This study was carried out using a low-frequency bio-potential amplifier with narrow bandwidth for use in QRS complex (part of the electrocardiogram which is a combination of the Q wave, R wave and S wave) detection systems. The architecture based on pseudo-resistors provides DC offset cancellation, adequate frequency response and a significant reduction of the signal recovery time. Both the pseudo-resistor and the QRS complex detector performance were experimentally measured with the temperature variation, in order to include this dependency in the PWL model. The transient recovery time, as well as the QRS complex detector frequency response, was also widely evaluated, in the proposed temperature range, through experimental measurements. The temperature dependence was added to the model and implemented in the SPICE simulation. The model outputs showed strong adherence to experimental data, showing a disagreement less than 6% in the low cut-off frequency. The macromodel’s response to the recovery time also followed the same experimental results behavior, presenting a maximum error of 20% within human body temperature range. The obtained recovery time was less than a normal heartbeat period to the entire temperature range evaluated. All of the analyzed circuits were implemented using GF 8HP 0.13 μm BiCMOS technology from Global Foundries.