Category: Digital Electronics

On February 9, 1907, one of Marconi’s engineers, Mr. H.J. Round of New York, NY, had a letter published in “Electrical World” magazine as follows: A Note on Carborundum To the editors of Electrical World: Sirs: During an investigation of the unsymmetrical passage of current through a contact of carborundum and other substances a curious…

Silicon is known as a four-valence semiconductor because it has four electrons available to make bonds in its outermost electron shell. Although silicon is the most commonly used semiconductor, there is another that requires some mention. The element gallium (chemical symbol Ga) has three electrons available in its outermost shell and the element arsenic (chemical symbol As)…

To illustrate the application of a transistor as a switch, first consider a simple circuit comprising a resistor and a real switch (Figure 10.8). Figure 10.8 Resistor-switch circuit (a) Circuit; (b) Waveform The labels VDD and VSS are commonly used in circuits employing MOSFETs. At this point we have little interest in their actual values and, for the purpose of…

Another family of transistors is known as metal-oxide semiconductor field-effect transistors (MOSFETs) of which there are two basic types called n-channel and p-channel; once again these names relate to the way in which the silicon is doped (Figure 10.7). Figure 10.7 Metal-oxide semiconductor field-effect transistors (MOSFETs) (a) NMOS field-effect transistor; (b) PMOS field-effect transistor In the case of these devices, the drain and source form…

More complex components called transistors can be created by forming a sandwich out of three regions of doped silicon. One family of transistors is known as bipolar junction transistors (BJTs) of which there are two basic types called NPN and PNP; these names relate to the way in which the silicon is doped (Figure 10.5). Figure 10.5 Bipolar junction transistors (BJTs); (a) NPN…

Most materials are conductors, insulators, or something in-between, but a special class of materials known as semiconductors can be persuaded to exhibit both conducting and insulating properties. The first semiconductor to undergo evaluation was the element germanium (chemical symbol Ge). However, for a variety of reasons, silicon (chemical symbol Si) replaced germanium as the semiconductor of choice.…