BIOPOTENTIAL AMPLIFIERS - Design and Development of Medical Electronic Instrumentation - page 17

Figure 1.15 erentially between positions Fp1 and Fp2 showing eyeblink EMG arti-

facts: (a) using an Ag/AgCl standard bioelectrode; (b) using the capacitive active bioelectrode. (Reprinted
from Prutchi and Sagi-Dolev [1993], with permission from the Aerospace Medical Association.)

EEG measured di ff

the driver circuit while reducing the e ff ective input cable capacitance by two orders of

magnitude. The fi first ampli fi cation stage has a gain determined by

R
R

5
4

G 1 1 11

C2 and R5 form a low-pass fi filter with a ( 3-dB) cuto ff frequency of 160 Hz, which stabi-

lizes the ampli er's operation. In addition, R1 and C1 (plus the capacitances of D1 and

D2) also form a low-pass

fi

fi filter, which further prevents oscillatory behavior and rejects

high-frequency noise.
The ampli fi ed signal is high-pass fi filtered by C3 and R13, with a ( 3-dB) cuto ff frequency

of 0.16 Hz, before being ampli fi ed by the second stage. The gain of this stage is set by

R
R

8
7

G 2 1 101