Digital To Analog Conversion Techniques Pdf Free

Digital to analog conversion techniques pdf free

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An analog-to-digital converter ADC performs the reverse function. There are several DAC architectures ; the suitability of a DAC for a particular application is determined by figures of merit including: resolution , maximum sampling frequency and others.

Digital to analog conversion techniques pdf free

Digital-to-analog conversion can degrade a signal, so a DAC should be specified that has insignificant errors in terms of the application. DACs are commonly used in music players to convert digital data streams into analog audio signals. They are also used in televisions and mobile phones to convert digital video data into analog video signals which connect to the screen drivers to display monochrome or color images. The audio DAC is a low-frequency, high-resolution type while the video DAC is a high-frequency low- to medium-resolution type.

Analog-to-Digital Conversion Pdf

Due to the complexity and the need for precisely matched components , all but the most specialized DACs are implemented as integrated circuits ICs. Discrete DACs circuits constructed from multiple discrete electronic components instead of a packaged IC would typically be extremely high speed low resolution power hungry types, as used in military radar systems.

Very high speed test equipment, especially sampling oscilloscopes , may also use discrete DACs. A DAC converts an abstract finite-precision number usually a fixed-point binary number into a physical quantity e.

In particular, DACs are often used to convert finite-precision time series data to a continually varying physical signal. An ideal DAC converts the abstract numbers into a conceptual sequence of impulses that are then processed by a reconstruction filter using some form of interpolation to fill in data between the impulses.

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A conventional practical DAC converts the numbers into a piecewise constant function made up of a sequence of rectangular functions that is modeled with the zero-order hold. Other DAC methods such as those based on delta-sigma modulation produce a pulse-density modulated output that can be similarly filtered to produce a smoothly varying signal.

As per the Nyquist—Shannon sampling theorem , a DAC can reconstruct the original signal from the sampled data provided that its bandwidth meets certain requirements e. Digital sampling introduces quantization error that manifests as low-level noise in the reconstructed signal. DACs and ADCs are part of an enabling technology that has contributed greatly to the digital revolution.

To illustrate, consider a typical long-distance telephone call. The caller's voice is converted into an analog electrical signal by a microphone , then the analog signal is converted to a digital stream by an ADC. The digital stream is then divided into network packets where it may be sent along with other digital data , not necessarily audio. The packets are then received at the destination, but each packet may take a completely different route and may not even arrive at the destination in the correct time order.

The digital voice data is then extracted from the packets and assembled into a digital data stream. A DAC converts this back into an analog electrical signal, which drives an audio amplifier , which in turn drives a loudspeaker , which finally produces sound. Most modern audio signals are stored in digital form for example MP3s and CDs and, in order to be heard through speakers, they must be converted into an analog signal.

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Specialist standalone DACs can also be found in high-end hi-fi systems. These normally take the digital output of a compatible CD player or dedicated transport which is basically a CD player with no internal DAC and convert the signal into an analog line-level output that can then be fed into an amplifier to drive speakers.

Similar digital-to-analog converters can be found in digital speakers such as USB speakers, and in sound cards.

Digital to analog conversion techniques pdf free

In voice over IP applications, the source must first be digitized for transmission, so it undergoes conversion via an ADC, and is then reconstructed into analog using a DAC on the receiving party's end.

Video sampling tends to work on a completely different scale altogether thanks to the highly nonlinear response both of cathode ray tubes for which the vast majority of digital video foundation work was targeted and the human eye, using a "gamma curve" to provide an appearance of evenly distributed brightness steps across the display's full dynamic range - hence the need to use RAMDACs in computer video applications with deep enough colour resolution to make engineering a hardcoded value into the DAC for each output level of each channel impractical e.

Given this inherent distortion, it is not unusual for a television or video projector to truthfully claim a linear contrast ratio difference between darkest and brightest output levels of or greater, equivalent to 10 bits of audio precision even though it may only accept signals with 8-bit precision and use an LCD panel that only represents 6 or 7 bits per channel. Video signals from a digital source, such as a computer, must be converted to analog form if they are to be displayed on an analog monitor.

A device that is distantly related to the DAC is the digitally controlled potentiometer , used to control an analog signal digitally.

Digital-to-Analog Converters

A one-bit mechanical actuator assumes two positions: one when on, another when off. The motion of several one-bit actuators can be combined and weighted with a whiffletree mechanism to produce finer steps.

Electronic Basics #10: Digital to Analog Converter (DAC)

The IBM Selectric typewriter uses such a system. DACs are widely used in modern communication systems enabling the generation of digitally defined transmit signals.

Digital to Analog Conversion

High-speed DACs are used for mobile communications and ultra high-speed DACs are employed in optical communications systems. The most common types of electronic DACs are: [2].

The most important characteristics of a DAC are: [ citation needed ]. Other measurements, such as phase distortion and jitter , can also be very important for some applications, some of which e.

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This trades greater quantisation distortion of loud signals for better performance of quiet signals. From Wikipedia, the free encyclopedia.

Digital to analog conversion techniques pdf free

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Digital to analog conversion techniques pdf free

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Digital to analog conversion techniques pdf free

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Digital to analog conversion techniques pdf free

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