
16 Operational amplifiers
16.1 Open loop amplifiers
The operational amplifier is a high-gain directly coupled voltage
amplifier, having a single output and two inputs, one inverting and
the other non-inverting. The output signal is proportional to the
differential signal voltage between the two input terminals, i.e.
VW
=
A
0
(V
X
- V
2
)
where A
Q
is the low-frequency open loop gain of the operational
amplifier, typically 10
5
. V
x
and V
2
are the two input voltages.
By grounding the positive (+) terminal (see Figure 16.1(a)) the
device can be used as a high-gain inverting amplifier. By grounding
the negative (-) terminal (see figure 16.1(b)) the devic ...