ADC: An Introduction To Analog To Digital Transverters?

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CHAPTER-1 INTRODUCTION 1.1 Introduction to ADC: Analog refers to physical quantities that vary continuously instead of discretely. The physical phenomena typically involve analog signals. We have many examples like speed, temperature, pressure, voltage, etc. But microprocessors work with digital quantities, means the values which are taken from discrete domain. To interact analog systems with digital systems or digital systems with analog systems conversion is needed. There are 2 types of conversions: (1) Analog to digital converters (ADCs), (2) Digital to analog converters (DACs). FIGURE1.Analog to Digital converter In the analog to digital converter the input vary from minimum to maximum value of volts or amperes. The output is a digital number that represents the input value. In the digital to analog converter the input that specifies an output whose value changes in steps. These step changes are in volts or amperes. Analog to digital conversion techniques have become extremely important. In this a great deal of technical effort has gone to produce analog to digital converters. Which are accurate, fast, and cheap. FIGURE2. Digital to Analog converter The ADC and DAC are together used in digital systems to provide complete interface for control systems with analog sensors and output devices. These type of systems are used in automotive engine controls. In this type of systems it is much easy to convert analog to digital signal and digital to analog signal. FIGURE3. Digital control system with analog I/O In the modern electronic systems, signal processing and storage are performed in the digital domain. For these type of systems conversions between analog and digital signals are required. In the adva... ... middle of paper ... ...ich are considered in analog to digital converter are current source, comparator and error sources. In a non ideal current source, the output impedance may be finite. In this case the value of current will be dependent on output voltage. Because of this we will introduce non-linearity to the entire ADC. This will reduce the non-linearity below the accepted level and imposed by the ADC resolution. In this situation the output impedance must be very high. Comparator is the most important part of the ADC. Why because the resolution of the comparator must be smaller than the ADC resolution, and also a reasonable speed is needed to get the minimum delay in the comparator. The delay of the comparator influences on the counter measured time. In the comparator design, there is one fact that the input common mode voltage varies for different levels of the input sample.

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