1. State Key Laboratory of Analog and Mixed-Signal VLSI, University of Macau, Taipa 999078, Macau
2. Department of Electrical and Computer Engineering, Faculty of Science and Technology, University of Macau, Taipa 999078, Macau
3. Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, CO 80045, USA
4. Department of Electrical Engineering, University of Colorado Denver, Denver, CO 80217-3364, USA