A Floating-Gate-Based Four-Channel Reconfigurable Analog Front-End Integrated Circuit

Abstract

In this paper, a four-channel floating-gate-based analog front-end (AFE) integrated circuit is presented. Each channel consists of a low noise amplifier (LNA), two operationaltransconductance-amplifier-capacitor (OTA-C) biquadratic filters, and two buffer amplifiers. Floating-gate transistors deployed in a two-dimensional array are utilized to facilitate circuit reconfigurability and to achieve better power efficiency. Floatinggate programming circuities are also designed on-chip. Furthermore, a serial-peripheral interface (SPI) circuit with floating-gate transistors as non-volatile memories is adopted as the circuit parameter storage as well as the control interface during floatinggate programming. A prototype chip is designed and fabricated in a 0.35 µm CMOS process, occupying an area of 13.62 mm 2 . The measured current consumption of a single sensing front-end channel is only 76 nA with the noise efficiency factor of 5.82. The measured output signal magnitude is 564.3 mVpp with 1% total harmonic distortion.

A Tunable Gain and Bandwidth Low-Noise Amplifier with 1.44 NEF for EMG and EOG Biopotential Signal

“…State-of-the-art LNAs for biopotential signal acquisition are typically composed of operational transconductance amplifiers (OTAs) presenting a fully differential capacitive feedback structure [5,6,[8][9][10][11][12][13][14][15]. This structure provides the LNA with a band-pass response where its mid-band gain can be easily set by the ratio between the input and feedback capacitors.…”

“…Moreover, by opting for a fully differential topology, it helps to achieve a high common-mode rejection ratio (CMRR) and power supply rejection ratio (PSRR) [8]. Some work further introduces the feedback loop pseudoresistors for better control in settling the LNA's BW [5,6,[8][9][10]13,14,16] or even provides BW tunability [8]. Another development carried out on the capacitive feedback loop was the introduction of reset switches to initialize or reset the input and output standard mode voltages before the amplifier starts or when it is saturated [16,17].…”

“…Table 1 presents the amplitude and frequency range characteristics of some common biopotential signals that can be recorded to detect diseases and monitor the patient's health [3]. Lowpower analog front-ends (AFEs) are used in the acquisition of such biopotential signals, which must comply with some sets of complex challenges, such as detecting the feeble biopotential signal while introducing minimum noise to the already weak signal for proper recording [4] and providing high linearity [5]. Moreover, portable AFEs have even more restrictions since they have very limited current budgets and, therefore, they have low power consumption to extend the operation lifetime while presenting small form factors to be ergonomic and, hence, fully benefiting from dedicated integrated circuit solutions.…”