Design of a Configurable 8-Channel Analog Front-End and Single-Ended 12-Bit SAR ADC for Biomedical Signal Acquisition on 180nm CMOS Process

In this work, a 8-channel Analog Front-End (AFE) circuit has been proposed for biomedical signal recording and converting. The AFE had a broad bandwidth, low noise, adjustable gain, high input impedance, could handle a variety of sensor inputs, and convert them to digital signal for biomedical recording systems. This design was developed based on the following blocks. The Buffer or Burrent-to-Voltage converter block (BCV), which could be set to operate as a buffer or a current-to-voltage converter circuit, achieved high input impedance and work with sensor signal types. A chopper capacitively-coupled instrumentation amplifier (CCIA) was as the main amplifier stage of the AFE to reduce input-referred noise and balance the impedance of the overall AFE system. A programmable gain amplifier (PGA) allowed the overall gain of the AFE to be adjusted. A Successive Approximation Register Analog-to-Digital Converter (SAR ADC) with Single-Ended algorithm structure permited the conversion of biomedical signals after preprocessing into a high-resolution digital sequence. The suggested AFE operated in a wide frequency range of 0.5 Hz to 2 kHz with a high input impedance bigger than 2TΩ. With the lowest 100-dB CMRR and low input-referred noise of 1.8 µVrms, the AFE can achieve low noise efficiency. Moreover, the SAR ADC had an rail-to-rail input range and an output resolution of 12-bit with a maximum sampling rate of 2.5-MS/s. The ADC achieved SNDR of 57.32dB, SFDR of 62.05dB, helping to ensure that the biomedical signal after converting to digital signal with high quality. The design incorporated new features such as the BCV, the IRN, the CMRR and the ADC to achieve the diverse functions of converting in comparison to prior research.