Open Access
Single-stage class-AB non-linear current mirror OTA
(IEEE, 2022) Beloso Legarra, Javier; Cruz Blas, Carlos Aristóteles de la; López Martín, Antonio; Institute of Smart Cities - ISC
The analysis, design and experimental characterization of a single-stage class-AB operational transconductance amplifier (OTA) with enhanced large- and small-signal performance is presented. The OTA is biased in weak inversion to save power and employs a non-linear current mirror as active load, leading a boosting current directly at the output branch. As a result, the amplifier's performance is improved without additional circuit elements and/or power consumption. A chip prototype has been fabricated in a 180-nm CMOS process, consuming a quiescent power of 2.5 µW from a supply voltage of ±0.5 V and a silicon area of 0.0013 mm 2 . For a load of 160 pF, it exhibits an average slew rate of 0.94 V/µs and a gain-bandwidth product of 22.1 kHz.
Open Access
Micropower class AB low-pass analog filter based on the super-source follower
(IEEE, 2022) Martincorena Arraiza, Maite; Cruz Blas, Carlos Aristóteles de la; López Martín, Antonio; Carlosena García, Alfonso; Institute of Smart Cities - ISC
An improved class AB version of the super source follower is used to implement a compact and power-efficient second order analog low-pass filter. The proposed circuit achieves a 41% power reduction as well as an improvement in linearity and pass band gain with respect to its class A counterpart. Measurement results of a test chip prototype fabricated in a 180 nm CMOS technology show a power consumption ranging from 50.3 μW to 85.27 μW for cutoff frequencies from 600 kHz to 890 kHz, with a supply voltage of ±0.75 V. A third order intermodulation distortion of −35.34 dB (for an input signal of 0.4 mV pp and 350 kHz) and a THD of −69.7 dB (for an input signal of 0.4 mV pp and 100 kHz) are measured, which results in an improvement with respect to the conventional class A version of 13.98 dB and 43.6 dB, respectively. The silicon area is 0.0592 mm 2 (using external capacitors).
Open Access
Low-voltage 0.81mW, 1-32 CMOS VGA with 5% bandwidth variations and -38dB DC rejection
(IEEE, 2020) López Martín, Antonio; Rico-Aniles, Héctor Daniel; Ramírez-Angulo, Jaime; Rocha-Pérez, José Miguel; González Carvajal, Ramón; Institute of Smart Cities - ISC
A CMOS low-voltage amplifier with approximately constant bandwidth and DC rejection is introduced. The design is based on the cascade of a wide linear input range OTA, an op-amp and a servo-loop with extremely large time constants. It operates with +/-0:45V supplies and a power consumption of 0.81mW in 180nm technology. The bandwidth changes only from 9.08MHz to 9.54MHz over a gain range from 1 to 32, it has a 9.8Hz low cutoff frequency and a DC attenuation of 38dBs. DC floating voltage sources are used to keep the gates of all differential pairs at a constant value close to a supply rail in order to operate the amplifier circuit with minimum supply voltage. The proposed circuit has small and large signal figures of merit FOMSS=5380 (MHz*pF/mW) and FOMLS=0:0085((V/ns)*pF/mA) for a nominal gain A=32.
Open Access
Analog lock-in amplifier design using subsampling for accuracy enhancement in GMI sensor applications
(MDPI, 2023) Algueta-Miguel, Jose M.; Beato López, Juan Jesús; López Martín, Antonio; Ciencias; Zientziak; Institute of Smart Cities - ISC; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, PJUPNA2005
A frequency downscaling technique for enhancing the accuracy of analog lock-in amplifier (LIA) architectures in giant magneto-impedance (GMI) sensor applications is presented in this paper. As a proof of concept, the proposed method is applied to two different LIA topologies using, respectively, analog and switching-based multiplication for phase-sensitive detection. Specifically, the operation frequency of both the input and the reference signals of the phase-sensitive detector (PSD) block of the LIA is reduced through a subsampling process using sample-and-hold (SH) circuits. A frequency downscaling from 200 kHz, which is the optimal operating frequency of the employed GMI sensor, to 1 kHz has been performed. In this way, the proposed technique exploits the inherent advantages of analog signal multiplication at low frequencies, while the principle of operation of the PSD remains unaltered. The circuits were assembled using discrete components, and the frequency downscaling proposal was experimentally validated by comparing the measurement accuracy with the equivalent conventional circuits. The experimental results revealed that the error in the signal magnitude measurements was reduced by a factor of 8 in the case of the analog multipliers and by a factor of 21 when a PSD based on switched multipliers was used. The error in-phase detection using a two-phase LIA was also reduced by more than 25%.
Open Access
Wide-swing class AB regulated cascode current mirror
(IEEE, 2020) Garde Luque, María Pilar; López Martín, Antonio; Cruz Blas, Carlos Aristóteles de la; Carvajal, Ramón G.; Ramírez-Angulo, Jaime; Institute of Smart Cities - ISC
A micropower regulated cascode CMOS current mirror is presented, combining floating gate and quasi floating gate MOS transistors to achieve both wide swing and class AB operation, respectively. Measurement results for a 0.5 μm CMOS test chip prototype are included, showing that the current mirror can provide a THD at 100 kHz of -44 dB for a supply voltage of ±0.75 V and input current amplitudes 20 times larger than the bias current.
Open Access
Two-stage OTA with all subthreshold MOSFETs and optimum GBW to DC-current ratio
(IEEE, 2022) Beloso Legarra, Javier; Grasso, A.; López Martín, Antonio; Palumbo, Gaetano; Pennisi, Salvatore; Institute of Smart Cities - ISC
An approach for the design of two-stage classAB OTAs with sub-1µA current consumption is proposed and demonstrated. The approach employs MOS transistors operating in subthreshold and allows maximum gain-bandwidth product (GBW) to be achieved for a given DC current budget, by setting optimum distribution of DC currents in the two amplifier stages. Following this strategy, a class AB OTA was designed in a standard 0.5-µm CMOS technology supplied from 1.6-V and experimentally tested. Measured GBW was 307 kHz with 980-nA DC current consumption while driving an output capacitance of 40 pF with an average slew rate of 96 V/ms
Open Access
Energy-efficient amplifiers based on quasi-floating gate techniques
(MDPI, 2021) López Martín, Antonio; Garde Luque, María Pilar; Algueta-Miguel, Jose M.; Beloso Legarra, Javier; González Carvajal, Ramón; Ramírez-Angulo, Jaime; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
Energy efficiency is a key requirement in the design of amplifiers for modern wireless applications. The use of quasi-floating gate (QFG) transistors is a very convenient approach to achieve such energy efficiency. We illustrate different QFG circuit design techniques aimed to implement low-voltage energy-efficient class AB amplifiers. A new super class AB QFG amplifier is presented as a design example including some of the techniques described. The amplifier has been fabricated in a 130 nm CMOS test chip prototype. Measurement results confirm that low-voltage ultra low power amplifiers can be designed preserving at the same time excellent small-signal and large-signal performance.
Open Access
Smart charging station with photovoltaic and energy storage for supplying electric buses
(IEEE, 2022) Berrueta Irigoyen, Alberto; Astrain Escola, José Javier; Puy Pérez de Laborda, Guillermo; El Hamzaoui, Ismail; Ursúa Rubio, Alfredo; Sanchis Gúrpide, Pablo; Villadangos Alonso, Jesús; Falcone Lanas, Francisco; López Martín, Antonio; Matías Maestro, Ignacio; Institute of Smart Cities - ISC
A Smart Charging Station (SCS) has been installed in the Public University of Navarre, Spain, in the framework of the H2020 Smart City Lighthouse STARDUST project. The SCS consists of a high-power electric bus charging point (300 kW), a 100 kW photovoltaic system, a 84 kWh support energy storage system based on a second-life lithiumion battery, and a monitoring and control system that allows the safe storage and convenient access to operation data. This SCS operates as a Smart Grid, being able to provide the power peaks required by the electric bus charger, reducing and smoothing the power demanded from the distribution grid and increasing the renewable energy self-consumption rate. This contribution presents a novel monitoring and control system, which is a key tool to integrate this SCS in the data infrastructure of a Smart City, as well as an energy management system able to operate the SCS to achieve the above-mentioned technical requirements. The crucial role of the monitoring and control system and the energy management system becomes evident in this work.
Open Access
AC coupled amplifier with a resistance multiplier technique for ultra-low frequency operation
(Elsevier, 2022) Martincorena Arraiza, Maite; Cruz Blas, Carlos Aristóteles de la; Carlosena García, Alfonso; López Martín, Antonio; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
This paper proposes a novel, tunable AC coupled capacitive feedback amplifier, exhibiting an ultra-low high pass corner frequency. This is accomplished by actively boosting the output resistive value of a MOS transistor in weak inversion. The circuit is based on a more general architecture, recently proposed by the authors, and is analyzed in terms of its capability to achieve ultra-low frequency operation, its DC performance, and noise. The proposed technique is demonstrated via measurement results from a fabricated test chip prototype using a standard 0.18 µm CMOS technology. The proposed amplifier provides a tunable high pass corner frequency from 20 mHz to 475 mHz, consuming 4.71 μW and a total area of 0.069 mm2.
Open Access
Fault detection of planetary gears based on signal space constellations
(MDPI, 2022) Martincorena Arraiza, Maite; Cruz Blas, Carlos Aristóteles de la; López Martín, Antonio; Molina Vicuña, Cristian; Matías Maestro, Ignacio; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
A new method to process the vibration signal acquired by an accelerometer placed in a planetary gearbox housing is proposed, which is useful to detect potential faults. The method is based on the phenomenological model and consists of the projection of the healthy vibration signals onto an orthonormal basis. Low pass components representation and Gram–Schmidt’s method are conveniently used to obtain such a basis. Thus, the measured signals can be represented by a set of scalars that provide information on the gear state. If these scalars are within a predefined range, then the gear can be diagnosed as correct; in the opposite case, it will require further evaluation. The method is validated using measured vibration signals obtained from a laboratory test bench.