Analog design versus digital design as a contemporary trend

Digital vs. Analog Design

The Trend toward Digital Design

When one choose between analog and digital design approaches, the relative merits of low cost analog vs. digital signal processing (DSP) solutions need to be explored.

Linear, or analog, circuits typically use only a few components, so are the simplest types of integrated circuits (IC). Usually, analog circuits are connected to devices that collect signals from the environment or send signals back to the environment, such as a microphone that converts fluctuating vocal sounds into an electrical signal of varying voltage (Integrated 5).

Investigating a system through studying its analog has been fairly common in science. In acoustics, the elements of various systems have been explained by setting up and studying a similar or analogous electrical system. Physics students recall elementary explanations of electrical phenomena in terms of easily visualized but analogous hydraulic phenomena, such as dams and locks with currents of water (Bianchi 1).

So it may be understood that an analog computer operates by setting up a (analogous) system that solves problems more easily but is so similar to the real system that the solution is valid for both. One of the oldest and most common analog computers is the slide rule. Marked along the sides in linear distance is a scale on the rule analogous or proportional to the logarithm of the numbers engraved. So setting the slides for multiplication of two numbers is equivalent to summing the logarithms of the two numbers.

People use analogous computing elements every day, such as the watthour meter which continuously determines the product of electrical voltage and current to arrive at power in watts and then integrates this with respect to time to obtain the energy used in watt hours.

In contrast, digital computers use numbers as discrete digital numbers, whole numbers or decimal fractions, while the analog computer represents mathematical quantities as an analogous continuous range of voltages.

Digital computers perform with numbers, working with only one arithmetic operation at a time, storing the result in memory and then proceeding to the next operation in the program. A digital computer is programmed by writing a set of instructions which will properly direct the computer at each step of the computation. Digital computing uses binary (only two numbers, zero and one) numbers to calculate complex sets of equations in simple sequences using these two numbers. Programing this sequence might be likened to reading a book. While a person will normally read each word and line one at a time, they may at times jump back to an earlier place in the text to confirm a fact, or skip sections not of interest. In a computer program, it may sometimes go back and repeat the instructions in some section of the program over and over again until some internal condition is met. This is called the flow of control within the program and it is what allows the computer to perform tasks repeatedly without human intervention.

These instructions, telling the computer to jump ahead or backwards to some other place in the program and to carry on executing from there, are called "jump" instructions (or branches). Jump instructions may be made to happen conditionally so that different sequences of instructions may depend on the result of something previous. Many computers directly support subroutines by providing a type of jump that "remembers" the location it jumped from and another instruction to return to that point. These programs require memory, as well as the information obtained from the calculations, in a digital computer.

The analog computer performs operations simultaneously, operating as a simulator. It may be operating on the same time scale as the real system being studied and the two may even be linked together. If all operations are performed simultaneously, the analog computer is faster than a digital computer of comparable cost. (Skagg xii).

Today there is a trend is toward digitally designed computing, rather than analogous problem solving, even though analogous is faster and takes less storage space. That is because of enormous improvements in the performance of integrated circuits and the cost reductions that rapid miniaturization has made in providing storage space in the digital computer.

As semiconductor chips have become more powerful and less expensive, they are becoming increasingly ubiquitous. And new capabilities are being added to chips. These include microelectromechanical systems (MEMs), "such as sensors and actuators, and digital signal processors that enable cost reductions and extend it into new types of devices. Examples of MEM devices include ink-jet printer cartridges, hard disk drive heads, accelerometers that deploy car airbags, and chemical and environmental sensors" (Gulliksen 2000).

Trends toward improvements in microelectronics and MEMs are expected to continue as well in information storage, networking and applications of information technology (it).

Information storage is necessary for a digital computer. Its process, not being analogous, need to be stored and then reused as the problem advances. Disk drives and other storage for information are improving in cost and performance. The amount of original information that can be stored has expanded so much that it is now estimated that most of the information in the world is now stored on various kinds of disk drives. And as the world wide web expands, this information has become increasingly available to everyone. Computers have improved incrementally with the amount of storage space made available, due to improvements in other areas, such as semiconductors, increasingly inexpensive and efficient microchips and the world-wide acceleration in the production of less expensive computers.

Networking is another reason for the trend in the growth of digital design, versus analogous design for computers. As computers connect to each other in networks, both wide area and local area networks, specialized software and hardware are becoming standardized and Internet based. As more people connect to the networks, the acceptance of the original digital design is becoming committed. Worldwide, there were 100 million Internet hosts or server computers connected to the Internet, in July of 2000, an increase from 30 million just two years earlier.

As the array of applications that make it more useful to everything from cars to individual computers to huge corporations, become more powerful and convenient, the use of digital design has left analogous design far behind. Originally, the digital computer was used primarily to process data, but their use expanded to word processing, spreadsheets and database programs. However, over the last twenty years, software has so improved and enabled applications, that uses have been expanded to "educational software, desktop publishing, computer-aided design and manufacturing, games, modeling and simulation, networking and communications software, electronic mail, the World Wide Web, digital imaging and photography, audio and video applications, electronic commerce applications, groupware, file sharing, search engines" and other applications (Significance 9).