Biomedical Engineering Reference
In-Depth Information
Offset Null
NC
Inverting
Input
Eight
Terminal
Operational
Amplifier
V+
Noninverting
Input
Output
V-
Offset Null
FIGURE 9.28
An eight-terminal operational amplifier. The terminal NC is not connected, and the two terminal
offset nulls are used to correct imperfections (typically not connected). V
þ
and V- are terminal power to provide
energy to the circuit. Keep in mind that a ground exists for both V
and V-, a ground that is shared by other ele-
ments in the circuit. Modern operational amplifiers have ten or more terminals.
þ
V
+
Inverting
Input
Output
Noninverting
Input
V
−
FIGURE 9.29
Circuit element symbol for the operational amplifier.
i
n
v
n
−
A (
v
p
−
v
n
)
−
R
+
v
o
i
A
i
p
+
v
p
FIGURE 9.30
An internal model of the op amp. The internal resistance between the input terminals, R, is very
large, exceeding 1 M
. The gain of the amplifier, A, is also large, exceeding 10
4
. Power supply terminals are omit-
Ω
ted for simplicity.
