SLEEVE-TACH DRIVE 9L9236 - Caterpillar

Introduction to Solid State Electrical Components
Modern electronic circuits use solid state components. Solid state electrical components are found in most Caterpillar machines.Semiconductors
Some elements, such as copper, are good conductors. Other elements are poor conductors, but good insulators. There are other elements that are neither good conductors nor good insulators. If an element falls into this group, but the element can be changed into a useful conductor, the element is called a semiconductor. Silicon and germanium are the most commonly used elements for semiconductors.Examples of semiconductors include diodes, transistors, and integrated circuits (ICs). Semiconductors are used throughout most Caterpillar machines. Semiconductors often replace mechanical switches.All semiconductors are solid state devices. A solid state device is one that can control current without moving parts, heated filaments, or vacuum bulbs. There are other solid state devices that are not semiconductors. A transformer is not a semiconductor.How Semiconductors Work
Illustration 1 g01072606
Pure semiconductors have tight electron bonding. There is no place for electrons to move. In this natural state, these elements are not useful for conducting electricity.However, semiconductors can be made into good conductors through doping. Doping is the addition of impurities. The impurities affect the free electrons in the semiconductor. Depending on which impurity is added, the resulting material will have either an excess of free electrons or a shortage of free electrons.If the added material creates an excess of free electrons, the semiconductor is negative or N type. If added material creates a shortage of free electrons, the semiconductor is positive or P type.Semiconductors are made from a sandwich of at least one slice of N type material and at least one slice of P type material. These slices are mounted inside a plastic or a metal housing. The area where the N type material and P type material meet is called the PN junction.Current Flow through Semiconductors
The flow of electricity through a semiconductor is different from other electrical devices. Usually, you define the movement of electricity as the movement of free electrons that bump each other from the negative terminal of the voltage source through the conductor and toward the positive terminal. When you discuss semiconductors, you describe not only the flow of electrons, but also the flow of holes. Holes are spaces in an electron shell to which an electron will be attracted.The flow of electrons is relatively easy to visualize. You can think of a flow of marbles through a channel, for example. The flow of holes is slightly harder to visualize.
Illustration 2 g01072607
Think of the same channel, that is filled with marbles, as shown in Illustration 2. One marble moves ahead, leaving a hole in the marbles place. The next marble moves into the position vacated by the first marble. At the same time, the hole can be said to be moving from the position that the first marble had held to the position that the second marble had held. As marbles move in one direction in the channel, holes can be said to be moving in the opposite