**Dual Slope and Successive ADC (Part-3)**

**Unit-06**

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A/D AND D/A CONVERTERS

Analog to digital convertor,

Digital to Analog Convertor,

ADC comparator,

Dual Slope ADC,

Successive ADC.

*ADC
comparator: - *

An
ADC comparator is a component of an analog-to-digital converter (ADC) that
compares the input analog signal to a reference voltage and generates a digital
output based on the result of the comparison.

The
comparator is the key element in determining the binary output of the ADC.

**The
operation of an ADC comparator is as follows: **

1. The **input analog signal** is compared
to a reference voltage using a high-gain amplifier, which is typically
implemented with an operational amplifier (op-amp).

2. If **the input voltage** is greater than
the reference voltage, the comparator outputs a high voltage (usually the
digital value '1'), indicating that the input voltage is higher than the
reference voltage.

3. If **the input voltage** is less than the
reference voltage, the comparator outputs a low voltage (usually the digital
value '0'), indicating that the input voltage is lower than the reference
voltage.

4. The **output of the comparator** is fed
into the digital logic circuitry of the ADC, which performs further processing
to generate the final digital output.

The
reference voltage can be a fixed voltage or a variable voltage that is adjusted
based on the input signal.

The
accuracy of the reference voltage is critical to the performance of the ADC,
and various techniques such as trimming and calibration are used to improve the
accuracy of the reference voltage.

The speed and accuracy of the ADC comparator are key factors in determining the performance of the ADC, and various techniques such as hysteresis, offset compensation, and input filtering are used to improve the performance of the comparator.

*Dual Slope ADC: -*

A
dual-slope ADC (analog-to-digital converter) is a type of integrating ADC that
is commonly used for low-speed and high-precision applications.

It
works by integrating the input signal for a fixed period of time and then
integrating a known reference voltage for a variable period of time until the
integrator output returns to zero.

The
process starts by resetting the integrator to zero and starting a
fixed-duration integration of the input voltage.

At
the end of this time period, the integrator output is transferred to a digital
counter.

The
counter is then enabled to count pulses from a clock source while the
integrator integrates a known reference voltage.

The
counter is stopped when the integrator output returns to zero, which occurs
after a variable period of time that is determined by the value of the input
voltage.

The
digital output of the counter represents the value of the input voltage, and
the integration time of the reference voltage is proportional to the input
voltage.

This
process of integrating the input voltage and the reference voltage for a fixed
and variable duration, respectively, is called dual-slope integration.

Dual-slope
ADCs are known for their high accuracy and low cost, but they are relatively
slow and require a stable reference voltage.

They
are widely used in applications such as digital mustimeters, data acquisition
systems, and process control.

*Successive ADC: -*

A
successive approximation ADC (analog-to-digital converter) is a type of ADC
that is commonly used in medium- to high-speed applications.

It
works by sequentially comparing the input voltage to a set of reference
voltages and using a binary search algorithm to determine the digital output.

The
conversion process starts by setting the most significant bit of the digital
output to 1 and the other bits to 0.

The
input voltage is compared to a reference voltage that is equal to half the
maximum analog input voltage.

If
the input voltage is greater than the reference voltage, the most significant
bit is left at 1, and the next reference voltage is set to the sum of the
previous reference voltage and half the remaining voltage range.

If
the input voltage is less than the reference voltage, the most significant bit
is set to 0, and the next reference voltage is set to the difference between
the previous reference voltage and half the remaining voltage range.

This
process is repeated for each bit of the digital output, with the reference
voltage being adjusted based on the previous comparison result.

The
result is a binary code that represents the input voltage with a resolution
that is determined by the number of bits used in the ADC.

Successive
approximation ADCs are known for their high speed, high resolution, and low
power consumption.

They
are widely used in applications such as data acquisition systems, medical
equipment, and digital audio.

**Analog to Digital Computer Part-01**

** Digital to Analog Convertor Part-2**

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