Biomedical Engineering Reference
In-Depth Information
EXAMPLE PROBLEM 9.19
Find the overall gain for the following circuit.
+
+
v
p
+
−
+
v
n
i
2
+
V
S
−
v
0
R
2
i
1
R
1
−−
−
Solution
Assuming the op amp is ideal, we start with
v
n
¼
v
p
. Then, since the op amp's noninverting
terminal is connected to the source,
v
n
¼
v
p
¼
v
s
. Because no current flows into the op amp, by
KCL we have
i
1
þ
i
2
¼
0
and
R
1
þ
v
s
v
o
v
s
R
2
¼
0
or
v
s
R
1
þ
R
2
R
1
v
o
¼
The overall gain is
v
s
¼
R
1
þ
R
2
v
o
R
1
This circuit is a noninverting op amp circuit used to amplify the source input. Amplifiers are
used in almost all clinical instrumentation for ECG, EEG, EOG, and so on.
