IEEE Circuits and Systems Magazine - Q1 2020 - 1

Circuits
and Systems
IEEE

MAGAZINE

Volume 20, Number 1

First Quarter 2020

Features

CMOS Transimpedance Amplifiers for Biomedical Applications:
A Comparative Study
Ahmed Atef, Mohamed Atef, Elsayed Esam M. Khaled, and Mohamed Abbas

Recently, different medical devices have emerged and utilized in a numerous health care fields such
as pulse oximetry, cuffless blood pressure using Photoplethysmogram (PPG), noninvasive blood
glucose measuring, and Near Infrared Spectroscopy (NIRS). Those devices are very similar in their
analog front end circuit which is a transimpedance amplifier (TIA). Many different TIA topologies have
appeared in different optoelectronic fields which make the choice of the best TIA topology for a certain
application a challenging task. In this regard, this paper presents a comparison between state of the
art, previously published TIA topologies. All topologies are simulated at four different simulation cases
to account for various design scenarios. The topologies are simulated with 10 pF photodiode (PD)
input capacitance and 5 kHz bandwidth (BW) while optimizing for two different targets; one time for
minimum input noise and the other for minimum power consumption. Moreover, the same procedures
are performed with 2 pF PD and 100 MHz BW to account for higher BW demanding applications. The
studied topologies are compared according to their transimpedance gain, power consumption, total
input referred noise current, and dynamic range (DR) to expose their relative merits. A noise and a
transimpedance gain mathematical models are also presented for each topology to assist the comparison. Recommendations to designers on which TIA to select in a certain application are concluded
according to the obtained results.
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An Alternative Path to Foster's Reactance Theorem and Its
Relation to Narrow-Band Equivalent Circuits
Bernhard Jakoby

Foster's seminal treatise on lossless networks has been published almost 100 years ago and a
particularly notable conclusion drawn therein, i.e. that the reactance (and susceptance) functions
are always monotonically increasing with frequency, is frequently referred to as Foster's theorem.
In this paper we present two variants for an alternative simple derivation of a stronger form of this
theorem, which holds for the driving point reactance (susceptance) of general lossless devices,
i.e. also configurations without lumped elements. One version introduces a realizable lumped element equivalent circuit approximating the considered circuit in a narrow band around a particularly
considered frequency. It turns out that this avenue of proof also facilitates an alternative validation
of the realizability of the so called Foster 1 and 2 realizations.

Adapted Compressed Sensing: A Game Worth Playing
Mauro Mangia, Fabio Pareschi, Riccardo Rovatti, and Gianluca Setti

Despite the universal nature of the compressed sensing mechanism, additional information on the
class of sparse signals to acquire allows adjustments that yield substantial improvements. In facts,
proper exploitation of these priors allows to significantly increase compression for a given reconstruction quality. Since one of the most promising scopes of application of compressed sensing is that of
IoT devices subject to extremely low resource constraint, adaptation is especially interesting when it
can cope with hardware-related constraint allowing low complexity implementations. We here review
and compare many algorithmic adaptation policies that focus either on the encoding part or on the
recovery part of compressed sensing. We also review other more hardware-oriented adaptation techniques that are actually able to make the difference when coming to real-world implementations. In
all cases, adaptation proves to be a tool that should be mastered in practical applications to unleash
the full potential of compressed sensing.

Printed in U.S.A.

Digital Object Identifier 10.1109/MCAS.2019.2961723

FIRST QUARTER 2020

IEEE CIRCUITS AND SYSTEMS MAGAZINE

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IEEE Circuits and Systems Magazine - Q1 2020

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