Book excerpt: IS THE TOPIC ANALOG TESTING AND DIAGNOSIS TIMELY? Yes, indeed it is. Testing and Diagnosis is an important topic and fulfills a vital need for the electronic industry. The testing and diagnosis of digital electronic circuits has been successfuIly developed to the point that it can be automated. Unfortu nately, its development for analog electronic circuits is still in its Stone Age. The engineer's intuition is still the most powerful tool used in the industry! There are two reasons for this. One is that there has been no pressing need from the industry. Analog circuits are usuaIly small in size. Sometimes, the engineer's experience and intuition are sufficient to fulfill the need. The other reason is that there are no breakthrough results from academic re search to provide the industry with critical ideas to develop tools. This is not because of a lack of effort. Both academic and industrial research groups have made major efforts to look into this problem. Unfortunately, the prob lem for analog circuits is fundamentally different from and much more diffi cult than its counterpart for digital circuits. These efforts have led to some important findings, but are still not at the point of being practicaIly useful. However, these situations are now changing. The current trend for the design of VLSI chips is to use analog/digital hybrid circuits, instead of digital circuits from the past. Therefore, even Ix x Preface though the analog circuit may be small, the total circuit under testing is large.