A COMPREHENSIVE SURVEY ON ANALOG FRONT-END CIRCUITS IN DIGITAL CONVERTERS WITH EMPHASIS ON BIOMEDICAL SENSOR APPLICATIONS

Abstract

 The standard of healthcare services is now being improved via biomedical applications, which are the focus of most technology progress. Since most biomedical equipment is rechargeable and portable, energy-efficient execution is required for all designs. Since analogue signals are the foundation of all communication, digital advancements can only occur when analogue signals can be converted into digital ones. In most biomedical devices, the analog-to-digital converter (ADC) is an essential component. Therefore, this review undergoes analogue front-end design (AFE) for biomedical sensor applications, and the design includes several modules, namely, amplifiers, filters, and ADC modules. This review highlights delta-sigma modulator (DSM) based ADC designs and Successive approximation registers (SAR) based ADC designs for biomedical sensor applications. Additionally, schematic views are provided for the three main ADC design building blocks: the comparator, the digital-to-analogue converter (DAC), and the sample and hold (S/H) circuit. In addition to this, the review undergoes several AFE designs, namely, Low-Noise Amplifier (LNA) and Programmable gain amplifier (PGA) Variable Gain Amplifier (VGA) for biomedical applications with diagrammatic representations. Numerous ADC design and amplifier parameters are eventually addressed in tabular form for improved comprehension. In addition to this, the challenges and future directions are discussed.