Digital to Analog Convertor and its type

Digital to Analog Convertor 

Unit-06

 

A/D AND D/A CONVERTERS

Analog to digital convertor,

Digital to Analog Convertor,

ADC comparator,

Dual Slope ADC,

Successive ADC.

 

Digital to Analog convertor: -

A digital-to-analog converter (DAC) is an electronic device that converts digital signals into analog signals.

DACs are commonly used in many applications, such as in audio equipment, video systems, and communication systems, to convert digital signals into analog signals for amplification, modulation, or transmission.

The digital signal is usually represented in binary form, and the analog signal is a continuous waveform that can be used to control an analog system.

The purpose of a DAC is to convert digital signals into analog signals so that they can be processed and used in analog systems such as audio equipment, video systems, and communication systems.

DACs are used in a wide range of applications, from simple devices such as digital thermometers to complex systems such as digital oscilloscopes.

The process of converting a digital signal into an analog signal involves two main steps: digital-to-analog conversion and analog filtering.

1.          Digital-to-Analog Conversion:

a.    This step involves converting the binary digital signal into a corresponding analog voltage or current.

b.    There are several methods for performing digital-to-analog conversion, including resistor ladder networks, binary-weighted resistor networks, and digital-to-analog converter integrated circuits (DAC ICs).

c.    The method used depends on the required precision, speed, and cost of the application.

2.          Analog Filtering:

a.    The output of the digital-to-analog conversion is a staircase-like waveform that contains a large amount of high-frequency noise.

b.    An analog filter is used to remove the high-frequency components and smooth out the waveform to obtain a continuous analog signal.

c.    The cut-off frequency of the filter is usually set to be below the highest frequency component of the signal.

The output of a DAC can be used to control various analog systems, such as speakers in an audio system, motors in a control system, and voltage-controlled oscillators in a communication system.

The performance of the DAC, such as its resolution, accuracy, and speed, determines the quality of the analog signal produced.

Types of DAC convertor : -

There are several types of digital-to-analog converters (DACs), each with its own advantages and disadvantages. The main types of DACs are:

1.          Resistor-String DAC:

a.    The resistor-string DAC is the simplest type of DAC and consists of a series of resistors with fixed values.

b.    Each resistor corresponds to a bit in the digital input, and the output voltage is determined by the sum of the voltages across the active resistors.

2.          R-2R Ladder DAC:

a.    The R-2R ladder DAC is a type of binary-weighted DAC that uses a ladder network of resistors to convert a binary digital input to an analog output.

b.    It has the advantage of using only two resistor values, which simplifies the manufacturing process.

3.          Delta-Sigma DAC:

a.    The delta-sigma DAC is a type of DAC that uses a delta-sigma modulator to convert a digital input to a high-frequency bitstream, which is then converted to an analog output using a low-pass filter.

b.    Delta-sigma DACs are known for their high accuracy and low noise, but they can be slow and have high latency.

4.          PWM DAC:

a.    The pulse width modulation (PWM) DAC converts a digital input to an analog output by generating a series of pulses with a variable width.

b.    The average value of the pulses is proportional to the input value, and a low-pass filter is used to smooth the output signal.

5.          Current-Output DAC:

a.    The current-output DAC generates an output current that is proportional to the digital input, which is then converted to an output voltage by an external resistor.

b.    Current-output DACs are widely used in applications such as motor control and audio amplifiers.

6.          Segmented DAC:

a.    The segmented DAC uses multiple segments, each with a different gain, to generate an output voltage that is proportional to the digital input.

b.    Segmented DACs are used in applications such as waveform generation and signal conditioning.

 

Block Diagram of Digital to Analog Convertor: -

 

1.              Digital Signal:

a.    The input to the DAC is a digital signal, which is typically represented in binary form.

b.    The digital signal can be generated by a digital system such as a computer, microcontroller, or digital signal processor.

2.              Digital-to-Analog Conversion:

a.    The digital signal is then converted into an analog signal by the DAC.

b.    This process involves converting the digital code into a corresponding analog voltage or current.

c.    The conversion is typically performed using a resistor ladder or a digital-to-analog converter integrated circuit (DAC IC).

3.              Low-pass Filter:

a.    The output of the DAC is a staircase-like waveform that contains a large amount of high-frequency noise.

b.    A low-pass filter is used to remove the high-frequency components and smooth out the waveform to obtain a continuous analog signal.

c.    The cut-off frequency of the filter is usually set to be below the highest frequency component of the signal.

4.              Analog Signal:

a.    The output of the DAC is an analog signal that represents the original digital signal.

b.    The analog signal can be further processed and amplified by analog circuits such as amplifiers and filters.

 

 Analog to Digital Computer Part-01

Dual Slope and successive ADC part-3