Author: workhouse123

In the BUF, NOT, AND, NAND, OR, and NOR gates described earlier, the input signals and internal data signals are only used to drive control terminals on the transistors. By comparison, transistors Tr3 and Tr4 in the XOR and XNOR gates shown above are connected so that input and internal data signals pass between their data terminals.…

The concepts of NAND, AND, NOR, and OR are relatively easy to understand because they map onto the way we think in everyday life. For example, a textual equivalent of a NOR could be: “If it’s windy or if it’s raining then I’m not going out.” By comparison, the concepts of XOR and XNOR can be a little harder to grasp…

A similar story occurs in the case of NOR gates and OR gates. First, consider a 2-input NOR, which requires four transistors (Figure 10.26). (A 3-input version could be constructed by adding an additional PMOS transistor in series with Tr1 and Tr2, and an additional NMOS transistor in parallel with Tr3 and Tr4.) Figure 10.26 CMOS implementation of…

The implementations of the NOT and BUF gates shown above illustrate an important point, which is that it is generally easier to implement an inverting function than its non-inverting equivalent. In the same way that a NOT is easier to implement than a BUF, a NAND is easier to implement than an AND, and a…

The simplest logic function to implement in CMOS is a NOT gate (Figure 10.20). The small circle, or bobble, on the control input of transistor Tr1 indicates a PMOS transistor. The bobble is used to indicate that this transistor has an active-low control, which means that a logic 0 applied to the control input turns the…

Three slightly more complex functions are known as AND, OR, and XOR (Figure 10.15). Figure 10.15 AND, OR, and XOR functions The AND and OR representations shown here are the abstract equivalents of our original switch examples. In the case of the AND, the output is only TRUE if both a and b are TRUE; in the case of the OR, the output is…

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…