Adc &dac ppt

ADC &DAC

Introduction• In electronics, a digital-to-analog converter (DAC or D-to-A) is a device that converts a

digital (usually binary) code to an analog signal (current, voltage, or electric charge). An analog-to-digital converter (ADC) performs the reverse operation. Signals are easily stored and transmitted in digital form, but a DAC is needed for the signal to be recognized by human senses or other non-digital systems.

• A common use of digital-to-analog converters is generation of audio signals from digital information in music players.

Analog :- • An analog signal is a continuous signal that contains time-varying quantities, such as

temperature or speed, with infinite possible values in between

• An analog signal can be used to measure changes in some physical phenomena such as light, sound, pressure, or temperature.

Sine Wave

Random- Periodic

Digital -:• Is a type of signal that can take on a set of discrete values (a quantized signal)

• Digital signals can represent a discrete set of values using any discrete set of waveforms .. And we can represent it like (0 or 1) ,( on or off )….. Etc

• Analog Signals: Continuous Infinite range of values More exact values, but more difficult

to work with

• Digital Signals Discrete Finite range of values Not as exact as analog, but easier to

work with

ADC

What is ADC?• An electronic integrated circuit which transforms a signal from analog (continuous)

to digital (discrete) form.

• Analog signals are directly measurable quantities.

• Digital signals only have two states. For digital computer, we refer to binary states, 0 and 1.

Why ADC is needed?• Microprocessors can only perform complex processing on digitized signals.

• When signals are in digital form they are less susceptible to the deleterious effects of additive noise.

• ADC Provides a link between the analog world of transducers and the digital world of signal processing and data handling.

There are two step Process-:

• Quantizing - breaking down analog value is a set of finite states

• Encoding - assigning a digital word or number to each state and matching it to the input signal

Quantizing -:

The number of possible states that the converter can output is: N=2n

(Where n is the number of bits in the AD converter)

Analog quantization size:Q= (V max -V min)/N

Sampling -:• It is a process of taking a sufficient number of discrete values at point on a waveform that will define the shape of waveform.• The more samples you take, the more accurately you will define the waveform.• It converts analog signal into series of impulses, each representing amplitude of the signal at given point…….

Types of A/D convertor :-

• Flash ADC • Digital-Ramp/Dual slope/Counter slope ADC• Successive Approximation ADC

Application of ADC• ADC are used virtually everywhere where an analog signal has to be processed, stored, or transported in

digital form.

• Some examples of ADC usage are digital volt meters, cell phone, thermocouples, and digital oscilloscope.

• Microcontrollers commonly use 8, 10, 12, or 16 bit ADCs, our micro controller uses an 8 or 10 bit ADC.

DAC

DACDAC:-• Digital-to-analog conversion is a process in which signals having a two defined levels or

states (digital (binary)) are converted into signals having a theoretically infinite number of states (analog (current, voltage, or electric charge)). A common example is the processing, by a modem, of computer data into audio-frequency (AF) tones that can be transmitted over a twisted pair telephone line. The circuit that performs this function is a digital-to-analog converter (DAC).

• Basically, digital-to-analog conversion is the opposite of analog-to-digital conversion. In most cases, if an analog-to-digital converter (ADC) is placed in a communications circuit after a DAC, the digital signal output is identical to the digital signal input. Also, in most instances when a DAC is placed after an ADC, the analog signal output is identical to the analog signal input.

DAC Types• The pulse-width modulator, the simplest DAC type.

• A stable current or voltage is switched into a low-pass analog filter with a duration determined by the digital input code.

• This technique is often used for electric motor speed control, but has many other applications as well.

Conclusion:-• The general smart concept was narrowed down to a specific goal: to improve the performance of

a high-speed, high-resolution ADC in terms of the speed/power/accuracy trade-off.

• Two key-factors were investigated that have the potential to enable high-performance AD converters for high-speed/high-resolution applications, namely:

• Open-loop circuitry.

• Time-interleaving.

• The smart concept was applied to DA converters with as aim to minimize the analog area as much as possible, and to use digital processing instead to solve the related accuracy problem.

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