To Study about the Power Converters & Digital Electronics.

• The analog input signal of ADC is continuous time & continuous amplitude signal. The output of ADC is a discrete time and discrete amplitude digital signal.
• In the real world, every real quantity such as voice, temperature, weight etc exists in the analog state. And it cannot be processed by any digital device such as a computer or a cell phone.
• These analog quantities are converted into digital form so that a digital device can process it. This conversion is done using analog to digital converter.

Block Diagram of ADC :

The analog signal is first applied to the ‘sample‘ block where it is sampled at a specific sampling frequency. The sample amplitude value is maintained and held in the ‘hold‘ block. It is an analog value. The hold sample is quantized into discrete value by the ‘quantize‘ block. At last, the ‘encoder‘ converts the discrete amplitude into a binary number.

Analog To Digital Conversion Steps -

The conversion from analog signal to a digital signal in an analog to digital converter is explained below using the block diagram given above.

Sample :

• The sample block function is to sample the input analog signal at a specific time interval. The samples are taken in continuous amplitude & possess real value but they are discrete with respect to time.
• The sampling frequency plays important role in the conversion. So it is maintained at a specific rate. The sampling rate is set according to the requirement of the system.

Hold :

• The second block used in ADC is the ‘Hold’ block. It has no function. It only holds the sample amplitude until the next sample is taken. The hold value remains unchanged till the next sample.

Quantize :

• This block is used for quantization. It converts the analog or continuous amplitude into discrete amplitude.
• The on hold continuous amplitude value in hold block goes through ‘quantize’ block & becomes discrete in amplitude. The signal is now in digital form as it has discrete time & discrete amplitude.

Encoder :

• The encoder block converts the digital signal into binary form i.e. into bits.
• As we know that the digital devices operate on binary signals so it is necessary to convert the digital signal into the binary form using the Encoder.
• This is the whole process of converting an Analog signal into digital form using an Analog to Digital Converter. This whole conversion occurs in a microsecond.

Application of ADC :

In the modern world of growing technology, we are dependent on digital devices. These digital devices operate on the digital signal. But not every quantity is in digital form instead they are in analog form. So an ADC is used for converting analog signals into digital signals. The applications of ADC are limitless. Some of these applications given below:

• Cell phones operate on the digital voice signal. Originally the voice is in analog form, which is converted through ADC before feeding to the cell phone transmitter.
• Images and videos captured using camera is stored in any digital device, is also converted into digital form using ADC.
• Medical Imaging like x-ray & MRI also uses ADC to convert images into Digital form before modification. They are then modified for better understanding.
• Music from the cassette is also converted into the digital form such as CDs and thumb drives using ADC converters.
• Digital Oscilloscope also contains ADC for converting Analog signal into a digital signal for display purposes & different other features.
• Air conditioner contains temperature sensors for maintaining the room temperature. This temperature is converted into digital form using ADC so that onboard controller can read & adjust the cooling effect.

In today’s modern world almost every device has become the digital version of itself & they need to have ADC in it. Because it has to operate in digital domain which can be only acquired using analog to digital converter (ADC).

• Digital to analog converter is an electronic circuit that converts any digital signal (such as binary signal) into an analog signal (voltage or current).
• The digital signal such as the binary signal exist in the form of bits & it is the combination of 1’s & 0’s (or High & low voltage levels). The DAC converts these bits into an analog voltage or current.
• The DAC has several digital inputs & a single analog output.

Need of DAC -

• The information exist in real world is in analog form. Why we convert them into digital form in the first place if we want to convert them back ?
• The processing speed of a digital computer is very fast & can compute or process any data in a matter of micro seconds. It conserves time & helps in processing complex data according to our need. But we cannot understand the digital data in real world.
• In order to understand the data that we process in a digital domain, we need to convert it into analog domain. An example of that would be the process of audio & video editing.
• We capture the data using our digital camera & microphone to convert the analog data into digital. We process it using our computers to edit it according to over needs. In order to view our edited work, we use DACs to convert it back into the analog domain to view & listen it through our screen & speakers.

PWM Based Conversion :

• It is another method used in digital to analog converter & microcontrollers such as Arduino can be easily programed to utilize its PWM function to generate an analog output.
• Pulse Width Modulation or PWM is a method of varying the average power of a signal by varying its duty cycle. He duty is the % turn on time of the signal, the % amount of time for which the signal remains high. Like 40% duty cycle signal means it stays high for 40% of time & stays low for 60%.
• We can use a binary number to generate such type signal whose duty cycle depends on the binary digit. The PWM wave is the filtered using a low pass filter to remove the fluctuations & provide a smooth analog voltage. 

Applications of DAC -

Digital to analog converters are used in various applications to convert a digitally processed signal into an analog signal. Some of the various applications of a DAC are given below :

 Audio :

• The audio signal is analog in nature but it is converted using ADC (analog to digital converter) into digital format to edit & store in storage devices in various digital formats such as mp3, wav etc.
• The audio amplifier or the sound card in a system contains DAC that converts the audio signal stored in digital device into an analog signal. The signal can be modified by the amplifier by varying its gain (volume), bass, treble etc. & then converted into analog signal because the speaker cannot support a digital signal.

Video :

• Digital video players utilize DAC to play any digital video using an analog monitor. These video players convert the digital signal from the digital source file into an analog signal.
• A digital video player has digital video ports such as DVI or HDMI. But if it has any analog output ports (composite port of yellow color), it contains a DAC whose job is to convert the video file into analog signal.

Motor Control :

• One of the most important components in controlling a motor using a digital device such as a microcontroller is a DAC.
• In various electronics projects, motor is embedded with a microcontroller. The microcontroller generates a digital signal to vary the speed of the motor which is converted into an analog signal using a DAC (Digital to Analog Converter).