Abstract
Utilizing R-2R ladders in design of active-RC approach promotes IC implementation of low frequency filters and leads to high linear and low power design solution for biomedical applications. However, area of R-2R ladders limits low frequency operation of this approach to few tens of Hz. This range is sufficient for designing 60 Hz powerline notch filter, but biomedical lowpass filers requires much lower pole frequencies. This paper investigates the use of other types of ladders (R-αR) in filter design. It shows that among various R-αR ladders, the R-0.5R ladders provide the most attractive solution for designing lowpass filters with ultra-low pole frequency. It is shown that R-0.5R ladders would require as low as 0.7 % of the area of R-2R ladders for realizing a given pole frequency. A second-order fully differential filter was fabricated in a standard 0.18 µm CMOS process. Experimental results showing cutoff frequency of around 1 Hz are provided.
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Deligoz, I., Naqvi, S. R., Copani, T., Kiaei, S., Bakkaloglu, B., Je, S., et al. (2011). A MEMS-based power-scalable hearing aid analog front end. IEEE Transactions on Biomedical Circuits and Systems, 5(3), 201–213.
Wong, A., Pun, K., Zhang, Y., & Nang Leung, K. (2008). A low-power CMOS front-end for photoplethysmographic signal acquisition with robust DC photocurrent rejection. IEEE Transactions on Biomedical Circuits and Systems, 2(4), 280–288.
Lee, S., & Cheng, C. (2009). Systematic design and modeling of a OTA-C filter for portable ECG detection. IEEE Transactions on Biomedical Circuits and Systems, 3(1), 53–64.
Corbishley, P., & Rodriguez-Villegas, E. (2007). A nanopower bandpass filter for detection of an acoustic signal in a wearable breathing detector. IEEE Transactions on Biomedical Circuits and Systems, 1(3), 163–171.
Li, K., & Warren, S. (2012). A wireless reflectance pulse oximeter with digital baseline control for unfiltered photoplethysmograms. IEEE Transactions on Biomedical Circuits and Systems, 6(3), 269–278.
Mollazadeh, M., Murari, K., Cauwenberghs, G., & Thakor, N. (2009). Micropower CMOS integrated low-noise amplification, filtering, and digitization of multimodal neuropotentials. IEEE Transactions on Biomedical Circuits and Systems, 3(1), 1–10.
Mollazadeh, M., Murari, K., Cauwenberghs, G., & Thakor, N. (2009). Wireless micropower instrumentation for multimodal acquisition of electrical and chemical neural activity. IEEE Transactions on Biomedical Circuits and Systems, 3(6), 388–397.
Rodríguez-Pérez, A., Ruiz-Amaya, J., Delgado-Restituto, M., & Rodríguez-Vázquez, Á. (2012). A low-power programmable neural spike detection channel with embedded calibration and data compression. IEEE Transactions on Biomedical Circuits and Systems, 6(2), 87–100.
Yazicioglu, R. F., Merken, P., Puers, R., & Hoof, C. V. (2008). A 200 uW eight-channel EEG acquisition ASIC for ambulatory EEG systems. IEEE Journal of Solid-State Circuits, 43(12), 3025–3038.
Sodagar, A., Perlin, G., Yao, Y., Najafi, K., & Wise, K. (2009). An implantable 64-channel wireless microsystem for single-unit neural recording. IEEE Journal of Solid-State Circuits, 44(9), 2591–2604.
Wong, A., Pun, K., Zhang, Y. T., & Hung, K. (2005). A near-infrared heart rate measurement IC with very lowcutoff frequency using current steering technique. IEEE Transactions on Circuits and Systems I, 52(12), 2642–2647.
Solis-Bustos, S., Silva-Martinez, J., Maloberti, F., & Sanchez-Sinencio, E. (2000). A 60 dB dynamic-range CMOS sixth-order 2.4 Hz low-pass filter for medical applications. IEEE Transactions on Circuits and Systems II, 47(12), 1391–1398.
Chen, C., Mak, P., Zhang, T., Vai, M., Mak, P., Pun, S., Wan, F., & Martins, R. P. (2009). A 2.4 Hz-to-10 kHz-tunable biopotential filter using a novel capacitor multiplier. In Asia Pacific Conference on Postgraduate Research in Microelectronics & Electronics (PrimeAsia 2009), China (pp. 372–375).
Hsu, C. L., Ho, M. H., Wu, Y. K., & Chen, T. H. (2006). Design of lowfrequency low-pass filters for biomedical applications. In Proceedings of IEEE Asia Pacific Conference on Circuits Systems, Singapore (pp. 690–695).
Alzaher, H., Tasadduq, N., & Mahnashi, Y. (2013). A highly linear fully integrated powerline filter for biopotential acquisition systems. IEEE Transactions on Biomedical Circuits and Systems, 7, 703–712.
Alzaher, H., Tasadduq, N., & Mahnashi, Y. (2013). Enhancing low frequency operation of active-RC filters employing R-2R networks. In International Conference on Technological Advances in Electrical, Electronics and Computer Engineering (TAEECE) (pp. 147–151).
Acknowledgments
The authors would like to acknowledge the support provided by King Fahd University of Petroleum & Minerals (KFUPM) and King Abdulaziz City for Science and Technology (KACST) through project No. AT-29-99.
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Alzaher, H.A., Algamdi, M.K. Employing R-0.5R networks in ultra-low bio-medical active-RC lowpass filters. Analog Integr Circ Sig Process 81, 407–416 (2014). https://doi.org/10.1007/s10470-014-0399-5
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DOI: https://doi.org/10.1007/s10470-014-0399-5