DESIGN AND DEVELOPMENT OF MEDICAL ELECTRONIC ...

8 BIOPOTENTIAL AMPLIFIERSIfRf-VccRinIinA-++VccVoutVinFigure 1.5Noninverting op-amp voltage amplifier; also known as a noninverting follower.-VCC-+Vin+VCCVoutFigure 1.6 A unity-gain buffer is a special case of the noninverting voltage amplifier in which theresistance ratio is R f /R in 0, which translates into unity gain. This configuration is often used in biomedicalinstrumentation to buffer a high-impedance signal source.ULTRAHIGH-IMPEDANCE ELECTRODE BUFFER ARRAYSA group of ultrahigh-impedance, low-power, low-noise op-amp voltage followers is commonlyused as a buffer for signals collected from biopotential electrode arrays. Thesecircuits are usually placed in close proximity to the subject or preparation to avoid contaminationand degradation of biopotential signals. The circuit of Figure 1.7 comprises 32 unity-gain