A 50μW Fully Differential Interface Amplifier With a Current Steering Class AB Output Stage for PPG and NIRS Recordings

This presents a low-power fully differential optical sensor interface amplifier for photoplethysmography (PPG) and near infrared spectroscopy (NIRS) recordings. The proposed amplifier employs a stacked current reuse input stage that provides a DC biasing voltage for the photodiode, reducing the parasitic capacitance. The output stage exploits a fully differential current steering class AB topology with a self-regulated common mode voltage, providing a <inline-formula> <tex-math notation="LaTeX">$70\mu \text{A}$ </tex-math></inline-formula> input current range with minimized quiescent current. Moreover, the interface amplifier can be reconfigured as either single-ended mode suitable for photo detectors biased at a high voltage or fully differential mode for those biased at a low voltage. This amplifier is implemented in a standard <inline-formula> <tex-math notation="LaTeX">$0.18\mu \text{m}$ </tex-math></inline-formula> CMOS process and characterized experimentally. Measurement results show that, with a 1.5V supply, the amplifier can provide up to 1V biasing voltage for the photodiode and consumes a static power of around <inline-formula> <tex-math notation="LaTeX">$50\mu \text{W}$ </tex-math></inline-formula>. It achieves a dynamic range of 97dB in fully differential mode with an input referred noise of 67pArms in 32Hz band and 102dB in single -ended mode with an input referred noise of 582pArms.

[1]  M. Sabarimalai Manikandan,et al.  Real-Time PPG Signal Quality Assessment System for Improving Battery Life and False Alarms , 2019, IEEE Transactions on Circuits and Systems II: Express Briefs.

[2]  A. Y. Bluestone,et al.  Near-Infrared Diffuse Optical Tomography , 2003, Disease markers.

[3]  Yuan-Ting Zhang,et al.  A 0.5-Hz High-Pass Cutoff Dual-Loop Transimpedance Amplifier for Wearable NIR Sensing Device , 2010, IEEE Transactions on Circuits and Systems II: Express Briefs.

[4]  Dong-Woo Jee,et al.  A <25 μW CMOS monolithic photoplethysmographic sensor with distributed 1b delta-sigma light-to-digital convertor , 2017, ESSCIRC 2017 - 43rd IEEE European Solid State Circuits Conference.

[5]  Chris J. M. Verhoeven,et al.  Influence of frequency compensation on the linearity of negative feedback amplifiers , 2005, 2005 IEEE International Symposium on Circuits and Systems.

[6]  Shuang Song,et al.  A Low-Voltage Chopper-Stabilized Amplifier for Fetal ECG Monitoring With a 1.41 Power Efficiency Factor , 2015, IEEE Transactions on Biomedical Circuits and Systems.

[7]  K. Glaros,et al.  A Sub-mW Fully-Integrated Pulse Oximeter Front-End , 2013, IEEE Transactions on Biomedical Circuits and Systems.

[8]  Luca Benini,et al.  A Multi-Sensor and Parallel Processing SoC for Miniaturized Medical Instrumentation , 2018, IEEE Journal of Solid-State Circuits.

[9]  Mario Konijnenburg,et al.  A 196μW, Reconfigurable Light-to-Digital Converter with 119dB Dynamic Range, for Wearable PPG/NIRS Sensors , 2019, 2019 Symposium on VLSI Circuits.

[10]  Yong Lian,et al.  Towards a Continuous Non-Invasive Cuffless Blood Pressure Monitoring System Using PPG: Systems and Circuits Review , 2018, IEEE Circuits and Systems Magazine.

[11]  Martin Wolf,et al.  Progress of near-infrared spectroscopy and topography for brain and muscle clinical applications. , 2007, Journal of biomedical optics.

[12]  Pedram Mohseni,et al.  A 1-V 8.1- $\mu$ W PPG-Recording Front-End With > 92-dB DR Using Light-to-Digital Conversion With Signal-Aware DC Subtraction and Ambient Light Removal , 2020, IEEE Solid-State Circuits Letters.

[13]  Refet Firat Yazicioglu,et al.  A Multi(bio)sensor Acquisition System With Integrated Processor, Power Management, $8 \times 8$ LED Drivers, and Simultaneously Synchronized ECG, BIO-Z, GSR, and Two PPG Readouts , 2016, IEEE Journal of Solid-State Circuits.

[14]  Mario Konijnenburg,et al.  A 665μW silicon photomultiplier-based NIRS/EEG/EIT monitoring asic for wearable functional brain imaging , 2018, 2018 IEEE International Solid - State Circuits Conference - (ISSCC).

[15]  Mario Konijnenburg,et al.  A 769 μW Battery-Powered Single-Chip SoC With BLE for Multi-Modal Vital Sign Monitoring Health Patches , 2019, IEEE Transactions on Biomedical Circuits and Systems.

[16]  Mohamed Atef,et al.  A Fully Integrated High-Sensitivity Wide Dynamic Range PPG Sensor With an Integrated Photodiode and an Automatic Dimming Control LED Driver , 2018, IEEE Sensors Journal.

[17]  John Allen.  Photoplethysmography and its application in clinical physiological measurement , 2007, Physiological measurement.