108335 Datasheet, PDF (16/21 Pages) Texas Instruments – Tiny CMOS Operational Amplifier with Rail-to-Rail Input and Output

Application Information (Continued)
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FIGURE 3. Cancelling the Effect of Input Capacitance
5.0 OUTPUT SWING
The output of the LMC7111 will go to within 100 mV of either
power supply rail for a 10 kΩ load and to 20 mV of the rail for
a 100 kΩ load. This makes the LMC7111 useful for driving
transistors which are connected to the same power supply.
By going very close to the supply, the LMC7111 can turn the
transistors all the way on or all the way off.
6.0 BIASING GaAs RF AMPLIFIERS
The capacitive load capability, low current draw, and small
size of the SOT23-5 LMC7111 make it a good choice for
providing a stable negative bias to other integrated circuits.
The very small size of the LMC7111 and the LM4040 refer-
ence take up very little board space.
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C_F and R_isolation prevent oscillations when driving capacitive loads.
FIGURE 4. Stable Negative Bias
7.0 REFERENCE BUFFER FOR A-TO-D CONVERTERS
The LMC7111 can be used as a voltage reference buffer for
analog-to-digital converters. This works best for A-to-D con-
verters whose reference input is a static load, such as dual
slope integrating A-to-Ds. Converters whose reference input
is a dynamic load (the reference current changes with time)
may need a faster device, such as the LMC7101 or the
LMC7131.
The small size of the LMC7111 allows it to be placed close to
the reference input. The low supply current (25 µA typical)
saves power.
For A-to-D reference inputs which require higher accuracy
and lower offset voltage, please see the LMC6462
datasheet. The LMC6462 has performance similar to the
LMC7111. The LMC6462 is available in two grades with
reduced input voltage offset.
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