Electronic Devices and Amplifier Circuits

Chapter 6Integrated CircuitsThis chapter begins with an introduction to electronic logic gates and their function in terms ofBoolean expressions and truth tables. Positive and negative logic are defined, and the transistor−transistorlogic (TTL), emitter−coupled logic (ECL), CMOS, and BiCMOS logic familiesare discussed. Earlier logic families are presented in the exercises section.6.1 Basic Logic Gates *Electronic logic gates are used extensively in digital systems and are manufactured as integrated circuits(IC’s). The basic logic gates are the inverter or NOT gate, the AND gate, and the OR gate, andthese perform the complementation, ANDing, and ORing operations respectively. The symbols forthese gates are shown in Figure 6.1.InverterFigure 6.1. The three basic logic gatesFour other logic gates, known as NAND, NOR, Exclusive OR (XOR), and Exclusive NOR (XNOR),are derivatives of the basic AND and OR gates and will be discussed later in this chapter.6.2 Positive and Negative LogicAND gateGenerally, an uncomplemented variable represents a logical 1 , also referred to as the true condition,and when that variable is complemented, it represents a logical 0 , also referred to as the false condition.Thus, if A = 1 (true), it follows that A = 0 (false). Of course, digital computers do not understandlogical 1 , logical 0 , true, or false; they only understand voltage signals such as that shown inFigure 6.2.0 volt ( ground) levelFigure 6.2. Typical voltage signal for a digital computerOR gate5 volt levelWith reference to the voltage waveform of Figure 6.2, integrated circuit manufacturers assign the letterH (High) to the 5 volt level and the letter L (Low) to the ground level as shown in Figure 6.3.* For this and the remaining chapters it is assumed that the reader has prior knowledge of the binary, the octal, andhexadecimal number systems, complements of numbers, binary codes, the fundamentals of Boolean algebra, and truthtables. If not, it is strongly recommended that a good book like our Digital Circuit Analysis and Design, ISBN 978−1−934404−05−8 is reviewed.Electronic Devices and Amplifier Circuits with MATLAB® / Simulink® / SimElectronics® Examples, Third EditionCopyright © Orchard Publications6−1