LMC6484AIM datasheet(15/22 Pages) NSC

15 / 22 page

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 V

S = ±5V.

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.

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.

DS011714-25

FIGURE 12. Inverting Configuration

Offset Voltage Adjustment

DS011714-26

FIGURE 13. Non-Inverting Configuration

Offset Voltage Adjustment

LMC6484AIM Datasheet(PDF) 15 Page - National Semiconductor (TI)