và thiên tai quần chúng. Những năm 1970 - tổ chức quốc tế và Mỹ chính thức trong pháp y nha khoa đã được thành lập. Tư pháp chấp nhận bằng chứng đánh dấu cắn burgeoned trong các tòa án Mỹ. | chapter 9 Design Practices Component matching and the protection from electrostatic discharge are important design practices. Accurate component matching reduces costs and improves circuit function. Protection from electrostatic discharge is a necessary precaution for reliability. Often chips are required to pass the human body model electrostatic discharge test discussed in this chapter. Matching While the absolute values of device parameters are difficult to maintain two devices can be accurately matched in a given circuit. This permits circuit design techniques to be used that result in accurate functions. In this section chip layout for accurate matching of components is discussed. Precise matching of components extends performance limits of circuits such as accurate voltage regulators or operational amplifiers with low input offset voltage. Laser trimming or zener zaping can extend performance limits but at the expense of test time and increased die area. Careful attention to matching can improve circuit performance reduce costs and increase design success. Component Size Edge irregularities become a significant fraction of device geometries for small-sized devices. Increasing size reduces the percent variability between matched components. The same unavoidable edge irregularities exist in large geometry devices as in small. However as shown in Figure for large geometries the percent variation due to edge irregularities is smaller. Therefore two large devices will match better than two small devices. If devices are very large the effects of lateral gradients cause the benefits of large devices to diminish. Figure Edge irregularities represent a larger fraction of device dimensions in small-sized devices. Orientation Matching improves when components are located close together and have the same orientation. This minimizes mismatch due to lateral process variations. Figure The resistors shown in A are oriented for the best match. C .
