Modern life depends on a few basic requirements and of these, one of the most important is digital electronics. In fact, it is difficult to imagine what would still be available to us if digital systems were removed. We would lose our computers, telephones, televisions. Radios, CDs and microwave ovens. Our transport system could not include modern ships, aircraft, trains and even many cars. As the day pass, we become more dependent on digital systems. On our planet digital devices outnumber us by more than a billion to one! It’s a good job they are friendly.
Digital electronics is very important to understand the working principle of wide range of equipment which we are using today. As the devices used in these applications decrease in size and employ more complex technology, it is essential for engineers and students to fully understand both the fundamentals and also the implementation and application principles of digital electronics, devices and integrated circuits, thus enabling them to use the most appropriate and effective technique to suit their technical needs.
Digital devices are based on electronic circuitry, which represent two states viz. ON or 1 (high) state and OFF or 0 (low) state. The ability to design integrated circuits consisting of several transistors, diodes, resistors, etc. on a thin wafer-small sized chip has made digital electronics a very feasible and potent technology. Digital circuits are used to store, evaluate and modify digital codes. Integrated circuits have made it possible t design circuits which are capable of handling large quantities of digital encoded data at enormously high speeds. The word digital means discrete units like the numbers of fingers, match sticks etc., which can express a whole number. Analog means establishing similarities between two quantities. Analog numbers are thus represented by directly measurable quantities such as voltage, current, resistance, etc. Examples of analog devices are voltmeter, ammeter, slide, rule, speedometer, etc. Both the systems- digital and analog are used in control systems, instrumentation, communications, computers and industrial automation. Digital methods of operation offer greater speed precision, accuracy and are more reliable and effective than analog methods. Digital methods are also less affected by noise as compared to analog methods. Moreover the information can be easily stored in digital systems.
Digital electronics is a special branch of Electronics in general and deals mainly with its digital components etc. The word ‘Digit’ in arithmetic means “position of a number”. However, now, ‘digital electronics’, numbers are expressed directly as only two digits ‘0’ and ‘1’. Normally, ‘Fingers” are also called as ‘Digits”. Therefore, each finger or digit represents a separate count. By counting, comparing and manipulating only these digits (‘0’ and ‘1’), or their combinations, according to a set of instructions, held on its’Memory’, a computer can perform a lot of works, such as analyse and organize vast amounts of business data, regulate the various operations of machines, control various stages of industrial processes, and even simple behavior of a number of dynamic systems like global weather patterns and complex chemical reactions in scientific research. In fact, applications of ‘digital electronics’ are increasing day and night, constantly and thus invading all walks of life.
The main reason for this unprecedented growth in “digital electronics”, is in the advent of digital ICs (Integrated Circuits). IC-technology has become so advanced, that complex digital circuits, like digital watches, memories, micro-processors and all the latest electronic equipment etc., comprising millions and millions of active and passive components, can be fabricated, on a tiny silicon-chip. The low cost and easy availability of these devices has resulted in their wide spread use.
Few areas of human endeavor have remained unaffected by electronics and many are even dominated by the seemingly my serious domain of this technology. Today we have the opportunity to work with electronic computers which are silently operating at fantastic speeds and solving complex problems. Modern medicine would be seriously handicapped without the availability of electronic instruments and aids as electronics equipment is extensively employed for diagnostic, monitoring and therapeutic applications. Recent years have seen the emergence of several new non-invasive medical imaging systems like ultrasonic scanners, computerized axial tomography and nuclear magnetic resonance systems which are basically dependent upon the ability of modern computers to handle enormous amount of data needed for picture reconstruction.