Data Converters


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All the real world quantities are analog in nature. We can represent these quantities electrically as analog signals. An analog signal is a time varying signal that has any number of values (variations) for a given time slot.

In contrast to this, a digital signal varies suddenly from one level to another level and will have only finite number of values (variations) for a given time slot.

This chapter discusses about the types of data converters and their specifications.

Types of Data Converters

The electronic circuits, which can be operated with analog signals are called as analog circuits. Similarly, the electronic circuits, which can be operated with digital signals are called as digital circuits. A data converter is an electronic circuit that converts data of one form to another.

There are two types of data converters

  • Analog to Digital Converter
  • Digital to Analog Converter

If we want to connect the output of an analog circuit as an input of a digital circuit, then we have to place an interfacing circuit between them. This interfacing circuit that converts the analog signal into digital signal is called as Analog to Digital Converter.

Similarly, if we want to connect the output of a digital circuit as an input of an analog circuit, then we have to place an interfacing circuit between them. This interfacing circuit that converts the digital signal into an analog signal is called as Digital to Analog Converter.

Note that some Analog to Digital Converters may require Digital to Analog Converter as an internal block for their operation.

Specifications

The following are the specifications that are related to data conversions −

  • Resolution
  • Conversion Time

Resolution

Resolution is the minimum amount of change needed in an analog input voltage for it to be represented in binary (digital) output. It depends on the number of bits that are used in the digital output.

Mathematically, resolution can be represented as

$$Resolution=\frac{1}{2^{N}}$$

where, ā€˜Nā€™ is the number of bits that are present in the digital output.

From the above formula, we can observe that there exists an inverse relationship between the resolution and number of bits. Therefore, resolution decreases as the number of bits increases and vice-versa.

Resolution can also be defined as the ratio of maximum analog input voltage that can be represented in binary and the equivalent binary number.

Mathematically, resolution can be represented as

$$Resolution=\frac{V_{FS}}{2^{N}-1}$$

where,

$V_{FS}$ is the full scale input voltage or maximum analog input voltage,

ā€˜Nā€™ is the number of bits that are present in the digital output.

Conversion Time

The amount of time required for a data converter in order to convert the data (information) of one form into its equivalent data in other form is called as conversion time. Since we have two types of data converters, there are two types of conversion times as follows

  • Analog to Digital Conversion time
  • Digital to Analog Conversion time

The amount of time required for an Analog to Digital Converter (ADC) to convert the analog input voltage into its equivalent binary (digital) output is called as Analog to Digital conversion time. It depends on the number of bits that are used in the digital output.

The amount of time required for a Digital to Analog Converter (DAC) to convert the binary (digital) input into its equivalent analog output voltage is called as Digital to Analog conversion time. It depends on the number of bits that are present in the binary (digital) input.

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