Biomedical Engineering Reference
In-Depth Information
equipment. For example, when the BPD is used in conjunction with an existing single-
ended ECG channel, J1-1 should be connected to the right-leg cable, and the other two
electrodes can be placed at convenient sites on the body.
DIFFERENTIAL AMPLIFIERS
When a di
erential voltage is applied to the input terminals of an op-amp as depicted in
Figure 1.20, the transfer function of the inverting follower must be rewritten as
ff
R
f
n
V
out
R
(
V
1
V
2
)
i
Similarly, the transfer function of the noninverting follower must be modi
fi
ed to
R
f
n
V
out
1
R
(
V
1
V
2
)
i
V
1
Vdiff
V
2
Vout
Vcm
Figure 1.20
Differential and common-mode voltages applied to the input of an op-amp.
R3
100K
+V
R1
10K
+
-
R2
10K
Vin
Vout
-V
R4
100K
R1=R2
R3=R4
Vout=(R3/R1)Vin
Figure 1.21
Differential amplifier implemented with an op-amp.
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