Application Information (Continued)
7.0 Offset Voltage Adjustment
Offset voltage adjustment circuits are illustrated in Figures
13, 14. Large value resistances and potentiometers are used
±
to reduce power consumption while providing typically 2.5
mV of adjustment range, referred to the input, for both con-
=
±
figurations with VS
5V.
DS011714-26
FIGURE 13. Non-Inverting Configuration
Offset Voltage Adjustment
8.0 Upgrading Applications
The LMC6484 quads and LMC6482 duals have industry
standard pin outs to retrofit existing applications. System
performance can be greatly increased by the LMC6484’s
features. The key benefit of designing in the LMC6484 is in-
creased linear signal range. Most op-amps have limited in-
put common mode ranges. Signals that exceed this range
generate a non-linear output response that persists long af-
ter the input signal returns to the common mode range.
DS011714-25
FIGURE 12. Inverting Configuration
Offset Voltage Adjustment
Linear signal range is vital in applications such as filters
where signal peaking can exceed input common mode
ranges resulting in output phase inversion or severe distor-
tion.
9.0 Data Acquisition Systems
Low power, single supply data acquisition system solutions
are provided by buffering the ADC12038 with the LMC6484
(Figure 14). Capable of using the full supply range, the
LMC6484 does not require input signals to be scaled down
to meet limited common mode voltage ranges. The
LMC6484 CMRR of 82 dB maintains integral linearity of a
±
12-bit data acquisition system to
0.325 LSB. Other
rail-to-rail input amplifiers with only 50 dB of CMRR will de-
grade the accuracy of the data acquisition system to only 8
bits.
15
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