Hot news

Digital Electronics Download PDF

Download Digital Electronics PDF
Digital Electronics PDF
Picture Of The Book :
Digital Electronics Download PDF

Contents Of The Book :

CHAPTER-1 Fundamental Concepts

1.1 ANALOG SIGNALS We are very familiar with analog signals. The reading of a moving coil or moving iron voltmeter and ammeter, dynamometer wattmeter, etc., are all analog quantities. The trace on a CRO screen is also analog. Analog methods for communication systems have long been in use. Frequency division multiplexing is the means of analog communication. An electronic amplifier is an analog circuit. The low-level analog signal (audio, video, etc.) is amplified to provide strength to the signal. Analog circuit systems (position control, process control) have been in use for the past many decades. Analog Computers use voltages, resistances, and potentiometric rotations to represent the numbers and perform arithmetic operations. Analog differentiation, integration, etc., is also done. The operational amplifier is a very versatile analog electronic circuit used to perform a variety of operations (addition, subtraction, multiplication, division, exponentiation, differentiation, integration, etc.). Analog integrated circuits are widely used in the electronic industry. 
1.2 DIGITAL SIGNALS The term digital is derived from digits. Any device or system which works on digits is a digital device or system. A digital voltmeter indicates the value of voltage in the form of digits, e.g., 230.25. Reading an analog instrument introduces human error and also requires more time. Digital reading is more accurate, eliminates human error, and can be read quickly. Communication systems have also gone digital. The initial signal waveform is always analog. To use digital transmission, the signal waveform is sampled and the digital representation is transmitted. The process of converting an analog signal to digital form is also known as digitizing. For multiple channels of transmission, Time Division Multiplexing is used. Digital control systems are fast replacing analog control systems. In digital control systems, the error is in the form of digital pulses. Digital computers have revolutionalized the concept of computers. Their capability ranges from simple calculations to complex calculations using numerical techniques. Many computing tasks which required hours and days take only a few minutes on digital computers. Digital signal processing is concerned with the representation of continuous-time (analog) signals in digital form. It is based on Claude Shannon’s∗ sampling theorem which states that “A band-limited continuous-time signal can be reconstructed in its entirety from a sequence of samples taken at intervals of less than 2fN 1 where fN is the highest frequency present in the signal.” The analog signal must be band-limited which limits how much it can change between samples. The sampling rate has too high to ensure accuracy. Since the initial signal is always analog and the final required signal is also mostly analog, a digital system requires three essential aspects (1) conversion of analog signal to digital form (2) transmission of digital signal (3) reconstruction of the analog signal from the received digital signal as shown in Fig. 1.1 A continuous time function x(t) is converted into a digital signal x(n) by an analog to digital (A/D) converter. The output of the discrete-time system is y(n) and is converted to a continuous time function by digital to analog (D/A) converter. The discrete-time system, in digital communications, is a digital communication channel. To achieve high fidelity, the sampling rate may have to be very high say 50000 samples per second. Each sample may be encoded by (say) 18 bits. The frequency fs (in Fig. 1.1) must be more than twice fN the highest frequency in the analog signal. Very-large-scale integration (VLSI) digital circuits can sample at a very fast rate so that high fidelity is achieved. 

Information Of The Book :

Title: Digital Electronics Download PDF
Language: English.
Size: 4,63 Mb.
Pages: 234.
Format: PDF.
Author:  Dr. Manoj Duhan