lmv111 National Semiconductor Corporation, lmv111 Datasheet - Page 7

• Manufacturer Part Number: lmv111
• Description: Operational Amplifier With Bias Network
• Manufacturer: National Semiconductor Corporation

Application Section
4.0 Phase Inverting AC Amplifier
A single supply phase inverting AC amplifier is shown in Fig-
ure 2 . The output voltage is biased at mid-supply, and AC in-
put signal is amplified by (R
input AC coupling capacitor to block DC potentials. A capaci-
tor of 0.1µF or larger can be used. The output of the LMV111
can swing rail-to-rail. To avoid output distortion, the
peak-to-peak amplitude of the input AC signal should be less
than V
It is recommended that a small-valued capacitor is used
across the feedback resistor R
lems, prevent peaking of the response, and limit the band-
width of the circuit. This can also help to reduce high fre-
quency noise and some other interference.
5.0 Fixed Current Source
A multiple fixed current source is show in Figure 3 . A refer-
ence voltage (V
by the voltage divider (R
used to cause the voltage drop across R
V
we neglect the base current of Q1 and Q2, essentially this
same current is available out of the collector of Q1. A Dar-
lington connection can be used to reduce errors due to the
bias current of Q1.
REF
. This controls the emitter current of transistor Q1 and if
CC
FIGURE 2. Phase Inverting AC Amplifier
(R
1
/R
2
REF
).
= 2.5V) is established across resistor R
3
2
and R
/R
2
1
). Capacitor C
to eliminate stability prob-
(Continued)
4
). Negative feedback is
1
to be equal to
IN
acts as an
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7
6.0 Difference Amplifier
The difference amplifier allows the subtraction of two volt-
ages or, as a special case, the cancellation of a signal com-
mon to two inputs. It is useful as a computational amplifier, in
making a differential to single-ended conversion or in reject-
ing a common mode signal.
FIGURE 3. Fixed Current Source
FIGURE 4. Difference Amplifier
DS101262-25
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