Figure 5 shows the same layout show

Figure 5 shows the same layout shown in Figure 3,plus a ground plane. It should be noted that the ground plane has a few breaks due to signal traces. These breaks should be kept to a minimum. Current return paths should not be “pinched” as a consequence of these traces restricting the easy flow of current from the device to the power connector. The histogram for the A/D Converter output is shown in Figure 6. Compared to Figure 4, the output codes are much tighter. The same active devices were used for both tests. The passive devices were different causing a slight offset difference.The noise shown with the A/D Converter digital code is assignable to the op amp noise and the absence of an anti-aliasing filter.