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
Bulk-driven CMOS linear transconductance-cell for AC amplifiers with very low cut-off frequency
(Elsevier, 2023) Ocampo-Hidalgo, Juan J.; Domínguez, Miguel Á.; 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
This manuscript proposes a novel linearized transconductor for AC amplifiers with a very low cut-off frequency. The cell uses an alternative solution that is based on a modified source-degeneration OTA, using two bulkdriven buffers, incorporating bootstrapping techniques to a buffer and a degenerated resistor. In the buffer, the bootstrapping effect is implemented by using a pseudo-resistor and a linear capacitor properly configured, whereas in the resistor the output voltages of the buffers are used with this goal. Thus, the proposed solution allows realizing a very large time constant, avoiding the use of very large size resistors and capacitors, thus saving chip area. The technique is demonstrated in an 0.18 μm CMOS technology by designing an OTA operating with a supply voltage of 0.6 V and achieving a low cut-off frequency of around 2 Hz with a power consumption of 462 nW.
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
CMOS low-voltage indirect current feedback instrumentation amplifiers with improved performance
(IEEE, 2020) Carrillo, Juan M.; Domínguez, Miguel Á.; Pérez Aloe, Raquel; Duque Carrillo, J. Francisco; Cruz Blas, Carlos Aristóteles de la; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
Indirect current feedback (ICF) is a very common operation principle used in the design of CMOS instrumentation amplifiers (IA). The input and output transconductors required in an ICF IA usually consist on resistive-degenerated simple differential pairs. In this contribution conventional source-follower (SF) structures used in IA transconductors are replaced by flippedvoltage-follower (FVF) and super-source-follower (SSF) cells, respectively. As a result, the overall performance and efficiency of the IA is enhanced with a minimum cost. The principle of operation governing CMRR is also analyzed and its behavior is confirmed by means of extensive simulations. A single-stage IA with a fixed voltage gain equal to 10 V/V has been designed in 0.35-μm standard CMOS technology to operate with 1.8 V supply. Simulation results show improved metrics in terms of voltage gain accuracy, while the overall performance of the IA is comparable to other contributions in the literature.

Cruz Blas, Carlos Aristóteles de la

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