Biomedical Engineering Reference
In-Depth Information
+15V
Va
IC1
OP-07
V
1
7 1
R6
3
R5
+
6
A1
2
-
10k, 0.1%
10k, 0.1%
R2
50k, 1.0%
4 8
-15V
-15V
J1
-
IN
IC3
OP-07
1
2
R1
1.0k, 1.0%
J2
4 8
2
V
+IN
-
out
6
1
2
A3
OUTPUT
3
+
7 1
-15V
R3
50k, 1.0%
+15V
IC2
OP-07
4 8
2
R4
R7
-
V
6
A2
3
+
10k, 0.1%
10k, 0.1%
7 1
Vb
+15V
Figure 1.26
Op-amp instrumentation amplifier.
ampli
er
, has the advantage of preserving the high input impedance of the noninverting
follower, yet o
fi
ff
ering gain. Input ampli
fi
ers A1 and A2 can be analyzed as noninverting
ampli
fi
ers which produce output voltages of
R
R
2
1
(R
R
2
)
V
2
V
A
1
V
1
1
and
R
R
3
1
(R
R
3
)
V
1
V
B
1
V
2
1
Initially, if it is assumed that the gain of ampli
fi
er A3 is unity and that R2
R3, then
V
out
V
B
V
A
Substituting into the two preceding equations gives the output voltage:
2
R
R
1
2
V
out
(
V
2
V
1
)
1
Whenever the gain of ampli
fi
er A3 is greater than unity, this equation must be multiplied
by the gain of the di
ff
erential stage. If R4
R5 and R6
R7, the overall voltage gain of
the instrumentation ampli
fi
er is given by
2
R
R
1
2
R5
V
out
(
V
2
V
1
)
1
Search WWH ::
Custom Search