9.3 Analog-to-digital and digital-to-analog conversion

Analog-to-digital and digital-to-analog conversion are crucial processes in modern electronics. They bridge the gap between the continuous analog world and the discrete digital realm, enabling devices to process and manipulate signals effectively.

These conversions involve sampling, quantization, and encoding steps. Understanding the trade-offs between sampling rate, resolution, and power consumption is key for engineers designing systems that balance performance and efficiency in various applications.

Analog-to-Digital and Digital-to-Analog Conversion

Process of analog-to-digital conversion

Top images from around the web for Process of analog-to-digital conversion

• 

  Analog To Digital Conversion - Sampling and Quantization - Electronics-Lab.com View original

  Is this image relevant?

• 

  Analog To Digital Conversion - Sampling and Quantization - Electronics-Lab.com View original

  Is this image relevant?

• 

  Analog To Digital Conversion - Sampling and Quantization - Electronics-Lab.com View original

  Is this image relevant?

• 

  Analog To Digital Conversion - Sampling and Quantization - Electronics-Lab.com View original

  Is this image relevant?

• 

  Analog To Digital Conversion - Sampling and Quantization - Electronics-Lab.com View original

  Is this image relevant?

1 of 3

Top images from around the web for Process of analog-to-digital conversion

• 

  Analog To Digital Conversion - Sampling and Quantization - Electronics-Lab.com View original

  Is this image relevant?

• 

  Analog To Digital Conversion - Sampling and Quantization - Electronics-Lab.com View original

  Is this image relevant?

• 

  Analog To Digital Conversion - Sampling and Quantization - Electronics-Lab.com View original

  Is this image relevant?

• 

  Analog To Digital Conversion - Sampling and Quantization - Electronics-Lab.com View original

  Is this image relevant?

• 

  Analog To Digital Conversion - Sampling and Quantization - Electronics-Lab.com View original

  Is this image relevant?

1 of 3

• Converts continuous-time, continuous-amplitude analog signal into discrete-time, discrete-amplitude digital signal
  • Analog signal varies continuously over time (voltage, current)
  • Digital signal consists of binary numbers representing analog signal's amplitude at discrete time intervals
• Key components:
  • Anti-aliasing filter removes high-frequency components from analog signal to prevent aliasing during sampling
  • Sample and hold circuit captures analog signal's amplitude at discrete time intervals and holds value constant for short period to allow quantization
  • Quantizer converts sampled analog value into discrete digital value by assigning it to nearest predetermined level
  • Encoder assigns unique binary code to each quantized level, producing final digital output

Process of digital-to-analog conversion

• Converts discrete-time, discrete-amplitude digital signal into continuous-time, continuous-amplitude analog signal
  • Digital signal consists of binary numbers
  • Analog signal varies continuously over time (voltage, current)
• Key components:
  • Digital input register holds binary code representing desired analog output level
  • DAC converter generates analog output level proportional to binary code in digital input register
    • Common DAC architectures: binary-weighted resistor, R-2R ladder, pulse-width modulation (PWM)
  • Reconstruction filter smooths stepped analog output from DAC converter, removing high-frequency components and reconstructing original analog signal

Comparison of ADC architectures

• Flash ADC:
  • Fastest architecture, suitable for high-speed applications
  • Uses parallel array of comparators to compare input signal with reference voltages simultaneously
  • Resolution limited by number of comparators (typically 8-12 bits)
  • High power consumption and complexity due to large number of comparators
• Successive Approximation Register (SAR) ADC:
  • Uses binary search algorithm to determine digital output one bit at a time
  • Requires only one comparator and a DAC, more power-efficient and less complex than flash ADC
  • Slower than flash ADC, but offers higher resolution (typically 12-18 bits)
  • Suitable for medium-speed, high-resolution applications
• Delta-Sigma ([object Object],[object Object]) ADC:
  • Oversamples input signal at high rate and performs noise shaping to push quantization noise to higher frequencies
  • Uses low-resolution ADC (typically 1-5 bits) and feedback loop with integrator and DAC
  • Achieves high resolution (16-24 bits) by trading off speed for accuracy
  • Suitable for low-speed, high-resolution applications (audio, precision measurement)

Trade-offs in ADC and DAC systems

• Sampling rate:
  • Higher rates allow more accurate representation of original analog signal and support wider signal bandwidth
  • Require faster ADC/DAC components, leading to increased power consumption and system complexity
• Resolution:
  • Higher resolution ADCs and DACs provide more precise digital representations of analog signal
  • Requires more complex circuitry, may result in slower conversion speeds and higher power consumption
• Power consumption:
  • Higher sampling rates and resolution typically lead to increased power consumption
  • Power-efficient architectures (SAR ADCs) can balance performance and power consumption
• System designers must consider application requirements and optimize trade-offs
  • Battery-powered devices: lower sampling rates and resolution may be acceptable to minimize power consumption
  • High-fidelity audio systems: higher sampling rates and resolution necessary to maintain signal quality, at cost of increased power consumption and system complexity