This ninth edition was introduced to bring the material up-to-date and to render all of the diagrams to the same standard. Some of the information from previous editions has been left out; either because it was obsolete or because it is not relevant to modern electronics. Most students are taught discrete component circuit analysis and design with silicon npn transistors as the main active devices. Although a flexibility of approach is important (. to be able to use both npn and pnp devices of any semiconductor type), the redrawn diagrams have been changed to conform to the npn silicon arrangement so that the learning process does not involve unfamiliar.
