arXiv subjects

Taeju Lee

Publications and source records attributed to Taeju Lee.

6 recordsLinked to original sources

arXiv2026

Frequency Synchronization Circuit Model for Analog Vector-Matrix Multiplication in the Frequency Domain

This work introduces a frequency synchronization circuit model for analog vector-matrix multiplication in the frequency domain. The frequency synchronization is implemented by coupling oscillators through all-to-all connections. Each oscillator is implemented using complementary cross-coupled transconductance pairs and RC high-pass filters. In this work, the frequency synchronization is achieved not only using oscillators alone but also through a configuration in which oscillators and resonator models (i.e., MEMS/NEMS resonators) are combined. While addressing the frequency synchronization of all the coupled oscillators, a partial synchronization is also discussed by controlling the coupling strength of a selected subset of oscillators. This frequency synchronization analysis focuses on the small-signal analysis using analog circuit and resonator models, thereby enabling an understanding of the synchronized frequency defined by the parameters of the analog circuit and resonator models.

physics.ins-det↗

arXiv2026

Oscillation with Negative Impedance

Oscillation and frequency modulation have been leveraged for applications in detection (or sensing), data processing, and telemetry. This work provides a theoretical analysis of oscillation phenomena with negative impedance implemented using a cross-coupled transconductance pair. The negative impedance can consist not only of a negative resistance but also of a negative inductance and a negative capacitance, where the negative resistance supplies energy to the inductance and capacitance, causing oscillation at a resonant frequency. Also, the resonant frequency can be modulated by combining with passive components such as a resistor, an inductor, and a capacitor. In this work, a comprehensive circuit analysis employing small-signal models and transfer functions is performed to understand the oscillation phenomena and resonant frequencies arising from a combination of active and passive RLC circuits, in which the active RLC circuit is modeled as a negative impedance and implemented using a cross-coupled transconductance pair.

physics.ins-det↗

arXiv2024

Analysis of Stability in Multistage Feedforward Operational Transconductance Amplifiers using Successive One-Pole Approximation

This paper presents analysis results of the operational transconductance amplifiers (OTAs) that combine feedforward paths and multistage amplifiers to achieve high-gain wideband operation as well as frequency compensation. To analyze multistage feedforward OTAs and provide an intuitive design method, the successive one-pole approximation (SOPA) is used for each substage of a multistage feedforward OTA. Using SOPA, the stability analysis is carried out from the two-stage feedforward OTA to the four-stage feedforward OTA in this work.

physics.ins-det↗

arXiv2023

Noise Analysis for Performance Evaluation of Biopotential Recording Front-Ends

Noise efficiency factor (NEF) and power efficiency factor (PEF) are widely used as the figure of merit to quantify the performance of biopotential recording front-ends. NEF and PEF are discussed from the noise analysis to the trend survey. To provide a comprehensive performance comparison of the front-ends, the performance mapping is developed using the design parameters of the technology node, NEF, PEF, |PEF - NEF|, and supply voltage. Using |PEF - NEF| provides how well a front-end balances between current-noise efficiency and power-noise efficiency, in other words, how biased a front-end is between current- and power-noise efficiencies. Also, the performance mappings of different front-end architectures are presented.

physics.ins-det↗

arXiv2023

Brief Architectural Survey of Biopotential Recording Front-Ends since the 1970s

Measuring the bioelectric signals is one of the key functions in wearable healthcare devices and implantable medical devices. The use of wearable healthcare devices has made continuous and immediate monitoring of personal health status possible. Implantable medical devices have played an important role throughout the fields of neuroscience, brain-machine (or brain-computer) interface, and rehabilitation technology. Over the last five decades, the bioelectric signals have been observed through a variety of biopotential recording front-ends, along with advances in semiconductor technology scaling and circuit techniques. Also, for reliable and continuous signal acquisition, the front-end architectures have evolved while maintaining low power and low noise performance. In this article, the architecture history of the biopotential recording front-ends developed since the 1970s is surveyed, and overall key circuit techniques are discussed. Depending on the bioelectric signals being measured, appropriate front-end architecture needs to be chosen, and the characteristics and challenges of each architecture are also covered in this article.

eess.SY↗

arXiv2023

Trend Investigation of Biopotential Recording Front-End Channels for Invasive and Non-Invasive Applications

This paper presents the trend of biopotential recording front-end channels developed from the 1970s to the 2020s while describing a basic background on the front-end channel design. Only the front-end channels that conduct electrical recording invasively and non-invasively are addressed. The front-end channels are investigated in terms of technology node, number of channels, supply voltage, noise efficiency factor, and power efficiency factor. Also, multi-faceted comparisons are made to figure out the correlation between these five categories. In each category, the design trend is presented over time, and related circuit techniques are discussed. While addressing the characteristics of circuit techniques used to improve the channel performance, what needs to be improved is also suggested.

eess.SY↗