[1] Y. Tokunaga, S. Sakiyama, A. Matsumoto and S. Dosho, "An On-Chip CMOS Relaxation Oscillator With Voltage Averaging Feedback," in IEEE Journal of Solid-State Circuits, vol. 45, no. 6, pp. 1150-1158, June 2010, doi: 10.1109/JSSC.2010.2048732.

[2] Lu, G., Pittet, P., Sou, G. et al. "A Novel Approach to Implementing On-Chip Synchronous Detection for CMOS Optical Detector Systems." Analog Integrated Circuits and Signal Processing 37, 57-66 (2003), doi: 10.1023/A:1024828902878

[3] Lecture Notes, EE6350 VLSI Design Laboratory. Dr. Peter Kinget, Columbia University in the City of New York, Spring 2022

[4] M. Tavakoli, L. Turicchia and R. Sarpeshkar, "An Ultra-Low-Power Pulse Oximeter Implemented With an Energy-Efficient Transimpedance Amplifier," in IEEE Transactions on Biomedical Circuits and Systems, vol. 4, no. 1, pp. 27-38, Feb. 2010

[5] R. Schaumann, M.E. Valkner, Design of Analog Filters, Oxford University Press, 2001.

[6] D. -H. Jang and S. Cho, "A 43.4uW photoplethysmogram-based heart-rate sensor using heart-beat-locked loop," 2018 IEEE International Solid-State Circuits Conference - (ISSCC), San Francisco, CA, USA, 2018, pp. 474-476, doi: 10.1109/ISSCC.2018.8310390.

[7] Z. Ebrahimi and B. Gosselin, "Ultralow-Power Photoplethysmography (PPG) Sensors: A Methodological Review," in IEEE Sensors Journal, vol. 23, no. 15, pp. 16467-16480, 1 Aug.1, 2023, doi: 10.1109/JSEN.2023.3284818.

[8] T. Delbruck and C. A. Mead, "Analog VLSI Phototransduction by continuous-time, adaptive, logarithmic photoreceptor circuits", California Institute of Technology, Sep. 2015.