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.

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.

DS101262-24

FIGURE 2. Phase Inverting AC Amplifier

DS101262-25

FIGURE 3. Fixed Current Source

DS101262-26

FIGURE 4. Difference Amplifier

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