DESIGN AND DEVELOPMENT OF MEDICAL ELECTRONIC ...

SINGLE-ENDED BIOPOTENTIAL AMPLIFIER ARRAYS 17Figure 1.15 EEG measured differentially between positions Fp1 and Fp2 showing eyeblink EMG artifacts:(a) using an Ag/AgCl standard bioelectrode; (b) using the capacitive active bioelectrode. (Reprintedfrom Prutchi and Sagi-Dolev [1993], with permission from the Aerospace Medical Association.)the driver circuit while reducing the effective input cable capacitance by two orders ofmagnitude. The first amplification stage has a gain determined byG 1 1 R 5 11R4C2 and R5 form a low-pass filter with a (3-dB) cutoff frequency of 160 Hz, which stabilizesthe amplifier’s operation. In addition, R1 and C1 (plus the capacitances of D1 andD2) also form a low-pass filter, which further prevents oscillatory behavior and rejectshigh-frequency noise.The amplified signal is high-pass filtered by C3 and R13, with a (3-dB) cutoff frequencyof 0.16 Hz, before being amplified by the second stage. The gain of this stage is set byG 2 1 R 8 101R7