ADC Part 3. The Progress of How to Convert Analog-to-Digital (ADC) to Digital-to-Analog (DAC).
Watch these video to understand more on Analog to Digital Conversion (ADC) & Digital to Analog Conversion (DAC)
• Analog to Digital Conversion (ADC) & ...
What is the Conversion Process of Analog-to-Digital (ADC) & Digital-to-Analog (DAC).
Part 1
What is Analog to Digital Conversion (ADC). Understand how Sampling Rate & No of Bits affect the ADC
• ADC Part 1. How to Decide the Samplin...
Part 2
ADC: Sampling Freq, No of Bits & Quantization Level, Quantization Step Size & Quantization Error
• ADC Part 2. Analog to Digital Convert...
Converting between Analog-to-Digital (ADC) and Digital-to-Analog (DAC) is essential in modern electronics, as many systems require processing analog signals in the digital domain or converting digital signals back to analog for various applications. Here’s a step-by-step explanation of the progress in how ADC and DAC systems work:
1. Analog-to-Digital Conversion (ADC)
The process of converting an analog signal to a digital signal involves three key steps:
Step 1: Sampling
Goal: Capture the continuous-time analog signal at discrete intervals.
Process: According to the Nyquist-Shannon Sampling Theorem, the sampling rate must be at least twice the highest frequency in the analog signal (called the Nyquist rate) to avoid aliasing.
Outcome: The analog signal is reduced to a series of discrete points, called samples.
Step 2: Quantization
Goal: Convert the amplitude of each sample to a finite set of levels.
Process: The continuous amplitude of each sample is rounded to the nearest level. These levels are determined by the resolution of the ADC (e.g., 8-bit, 12-bit, 16-bit). The number of possible quantization levels is 2𝑁
N is the bit resolution.
Outcome: Each sample is assigned a digital value, with an inherent quantization error (the difference between the true analog value and the quantized digital value).
Step 3: Encoding
Goal: Represent the quantized samples as binary values.
Process: Each quantized level is encoded as a binary number. The number of bits required depends on the resolution of the ADC.
Outcome: A stream of binary numbers representing the original analog signal at discrete intervals.
2. Digital Processing
Once the analog signal is digitized through ADC, it can be processed digitally using computers, digital filters, microcontrollers, or DSP (Digital Signal Processing) systems. Digital processing allows for data storage, compression, filtering, modulation, or other manipulation that would be difficult to achieve in the analog domain.
3. Digital-to-Analog Conversion (DAC)
After processing the digital signal, converting it back into an analog form is often required, especially for audio, video, or control applications. The steps of DAC mirror those of ADC but in reverse:
Step 1: Binary Data to Quantized Levels
Goal: Convert the binary-encoded digital data back into corresponding voltage or current levels.
Process: Each binary number from the digital signal is converted into its corresponding analog level based on the resolution (just like in ADC but reversed). For example, an 8-bit DAC can generate 256 distinct voltage or current levels.
Outcome: A series of quantized levels that represent the digital data in an analog form.
Step 2: Reconstruction
Goal: Convert the quantized levels into a continuous analog signal.
Process: The output from the DAC is typically a step-like signal, as it consists of discrete levels. To smooth the signal and remove the high-frequency components introduced by quantization, a low-pass filter (often called a reconstruction filter) is applied. This filter smooths out the transitions between discrete levels, effectively reconstructing the continuous waveform.
Outcome: A continuous-time analog signal that approximates the original signal before it was digitized by ADC.
Illustration of ADC to DAC Process
Original Analog Signal:
A continuous waveform (e.g., audio signal or temperature measurement).
ADC (Analog-to-Digital Conversion):
Sampling: Takes samples at regular intervals.
Quantization: Rounds each sample to the nearest digital level.
Encoding: Converts the quantized values into binary numbers (e.g., 10101101).
Digital Domain:
Processing: Binary data can now be manipulated (e.g., filtered, compressed, or stored).
DAC (Digital-to-Analog Conversion):
Binary Data to Quantized Levels: Converts binary values back into voltage/current levels.
Reconstruction Filter: Smooths the output to form a continuous analog signal.