Open Access
AC amplifiers with ultra-low corner frequency by using bootstrapping
(Institution of Engineering and Technology, 2021) Martincorena Arraiza, Maite; Carlosena García, Alfonso; Cruz Blas, Carlos Aristóteles de la; López Martín, Antonio; Ingeniería Eléctrica y Electrónica; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
A novel architecture for an AC (i.e. high-pass) amplifier is proposed allowing a drastic reduction of the cutoff frequency to the sub-Hertz range. It builds upon the classic AC configuration with a high gain amplifier and a parallel RC circuit in the feedback loop, by increasing the feedback resistance through bootstrapping. Resistance multiplying factors higher than four orders of magnitude are easily achievable. The basic principle can be applied to several practical implementations, though in this letter it is demonstrate with measurement results of an op-amp based discrete implementation.
Open Access
High-linearity tunable low-Gm transconductor based on bootstrapping
(IEEE, 2021) Cinco-Izquierdo, Óscar J.; Cruz Blas, Carlos Aristóteles de la; Sanz-Pascual, M. Teresa; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
In this brief, a novel pseudo-differential low-transconductance amplifier is proposed based on the bootstrapping technique. The transconductor is implemented using two voltage follower topologies as amplifiers with their outputs connected to both terminals of a resistor, thus bootstrapping the voltages at these terminals to increase the equivalent resistance value, and achieve a very low transconductance without the need for large passive components. In this way, a highly-linear compact structure is designed whose transconductance can be tuned by external current sources. The circuit was fabricated in a standard 0.18μm CMOS process. The experimental results show a tunable transconductance in the range of tens of nA/V, with a total harmonic distortion lower than -40dB at 350mVpp@1kHz. The power consumption of the amplifier is 4μW under a 1.8V supply voltage.
Open Access
Low-voltage CMOS bulk-driven buffer with bootstrapping technique for gain enhancement and THD-noise reduction
(IEEE, 2022) Cruz Blas, Carlos Aristóteles de la; Carrillo, Juan M.; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
In this paper, a bootstrapping technique is applied to a bulk-driven voltage buffer for canceling the gate-source transconductance in order to improve the cell gain, the linearity and reduce the input-referred noise. The bootstrapped circuitry is conveniently implemented by only using a capacitor and a pseudo resistor. The suitability of the technique is demonstrated by simulation results using a flipped voltage follower, even though it is general and can be applied to other structures. A 1-V buffer is designed in 0.18 µm CMOS technology, showing a 4.3 times improvement in the voltage gain (conventional 0.21 V/V, bootstrapped 0.90 V/V), increasing 5 times the input voltage range for a 1% THD (conventional 50 mV, bootstrapped 250 mV) and reducing the input equivalent noise around a 16% (conventional 180 nV/-√Hz, bootstrapped 155 nV/√Hz at 10 kHz).
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.
Open Access
Experimental teaching of digital PID controllers
(IEEE, 2024-08-01) Tainta Ausejo, Santiago; Cruz Blas, Carlos Aristóteles de la; Cid Monjaraz, Jaime; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza
PID controllers are a fundamental building block of industrial control systems. In this paper we present a simple demonstrator that can be assembled using basic electronic components and an Arduino UNO development board as plant and digital controller, respectively. The complete system can be easily built using components that are often available in a basic electronic lab, avoiding mechanical or electromechanical systems. The proposed system is open and flexible, allowing the study of digital PID control systems and the experimental evaluation of different tuning methods.
Open Access
0.6-V CMOS bulk-driven instrumentation amplifier for IoMT bioimpedance analysis
(Wiley, 2024) Carrillo, Juan M.; Ocampo-Hidalgo, Juan J.; Corbacho, Israel; Cruz Blas, Carlos Aristóteles de la; Domínguez, Miguel Á.; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC
An instrumentation amplifier (IA), aimed at wideband bioimpedance analysisin the low-voltage low-power scenario of internet of medical things (IoMT), ispresented. The operation principle is based on the indirect current feedbacktechnique, where an input and a feedback transconductor determine thevoltage gain of the preamplifier. The required transconductors consist of twobulk-driven flipped-voltage-follower cells and an active pseudo-resistor, thusleading to a linear and compact implementation. The circuit has been designedand fabricated in 180 nm CMOS technology to operate with a 0.6-V supply.Experimental results obtained from measurements on eight samples of thesilicon prototype show that when the IA is programmed to have a nominalvoltage gain of 11 V/V, the bandwidth is 316.2 kHz, the CMRR exceeds63 dB, and the maximum output voltage that can be processed with a THDbelow –40 dB is 555 mVpp.
Open Access
Low-power ultrasonic front-end for cargo container monitoring
(IEEE, 2019) Algueta-Miguel, Jose M.; García Oya, José Ramón; López Martín, Antonio; Cruz Blas, Carlos Aristóteles de la; Muñoz Chavero, Fernando; Hidalgo Fort, Eduardo; Institute of Smart Cities - ISC
A low-power ultrasonic communication system conceived for cargo container monitoring is presented. Two piezoelectric transducers operating at 40 kHz are used for generating and acquiring an ultrasonic signal through the metallic wall, thus establishing a non-invasive inside-outside communication that preserves the container integrity. Both transducers are fixed by means of a novel magnetic case designed for optimizing data transmission. The acoustic and electrical characteristics of the ultrasonic channel are analyzed. An experimental measurement setup based on FPGA has been implemented for comparing some basic modulation and detection schemes in terms of Bit Error Rate (BER), also considering their robustness against undesired mechanical and electromagnetic perturbations. On this basis, a compact digital DBPSK modulator using a square carrier signal is proposed. Frequency and amplitude tracking algorithms are designed for optimizing the quality and robustness of the data transmission. Finally, a low-power low-rate (up to few kbps) architecture based on the previous elements is presented. All the proposed contributions are experimentally validated.
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
Low-power wide-bandwidth CMOS indirect current feedback instrumentation amplifier
(Elsevier, 2020) Carrillo, Juan M.; Domínguez, Miguel Á.; Pérez Aloe, Raquel; Cruz Blas, Carlos Aristóteles de la; Duque Carrillo, J. Francisco; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
The analysis and design trade-offs of a simple and economical technique to implement wideband low-voltage CMOS instrumentation amplifiers (IAs) based on indirect current feedback (ICF), are described. The input and an output transconductors consist of two super-source-followers and a resistor. As a result, the overall performance of the IA is enhanced. A thorough analysis of the proposed technique provided valuable insight on its operation. Two different realizations in 0.35-μm CMOS technology of an IA operating with a supply voltage of 3 V, are presented. In particular, a wide bandwidth single-stage IA with fixed voltage gain equal to 50 V/V and a low-power two-stage IA with externally programmable voltage gain, have been designed and characterized by extensive simulations. The simulated results of both circuits showed an improved response in terms of bandwidth, noise and power consumption, while their overall performance is comparable to other proposed approaches in terms of common-mode rejection ratio (CMRR) and linearity (THD).
Open Access
Gain-boosted super class AB OTAs based on nested local feedback
(IEEE, 2021) Beloso Legarra, Javier; Cruz Blas, Carlos Aristóteles de la; López Martín, Antonio; Ramírez-Angulo, Jaime; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica
A new approach to design super class AB operational transcon-ductance amplifiers (OTAs) with enhanced large-signal and small-signal performance is presented. It is based on employing two nested positive and negative feedback loops at the active load of an adaptively biased differential pair in weak inversion region. As a result, DC gain, gain-bandwidth product, settling time and noise are improved compared to conventional super class AB OTAs without extra circuit nodes or power consumption. Measurement results of a 180 nm CMOS test chip prototype show a current boosting factor higher than 5000 and a nearly ideal current efficiency. Due to the ultra-low quiescent currents and high driving capability, the circuit exhibits an excellent large-signal figure-of-merit (FOML) of 236 V-1. To illustrate the applicability of the proposed approach, a differential sample-and-hold (S/H) circuit was designed and fabricated on the same test chip. Measurement results of the S/H validate the advantages of the proposal.