1.The design of a high-performance, full-custom integrated circuit (IC) is, of course, a difficult task. In full-custom IC design, everything, down to and including individual transistors may be designed (although libraries of parts are, of course, used).
2.For many years, however, it has been possible to build semi-custom integrated circuits using gate arrays. A gate array, as its name suggests, is an integrated circuit on which an array of gates has been created. The design of an application-specific integrated circuit (ASIC) using a gate array therefore involves the definition of how the gates in the array should be connected.
3.In practical terms, this means that one or two layers of metal interconnect must be designed. Since an integrated circuit requires seven or more processing stages, all the processing steps other than the final metalization can be completed in advance. Because the uncommitted gate arrays can be produced in volume, the cost of each device is relatively small.
4.A diode is reverse biased when the diode negative electrode voltage is higher than the anode electric potential. The diode internal resistance was extremely high by now.
5.There are four basic tests required for transistors in practical applications: gain, leakage, breakdown, and switching time. All of these tests are best made with commercial testers or oscilloscopes.