13: Digital-Analog Conversion
- Page ID
- 993
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- 13.1: Introduction to Digital-Analog Conversion
- This page covers the interface between digital circuitry and sensors, emphasizing the ease of connecting digital sensors like switches and encoders. It explains that interfacing with analog devices is more challenging, requiring analog-to-digital converters (ADCs) for conversion and digital-to-analog converters (DACs) for the opposite.
- 13.2: The R/2nR DAC- Binary-Weighted-Input Digital-to-Analog Converter
- This page describes the R/2nR DAC circuit, which is a binary-weighted-input digital-to-analog converter (DAC) using an inverting summing op-amp with varying resistors (R, 2R, 4R). It produces output voltages proportional to digital binary inputs, reflecting the binary counting system. The circuit is adjustable and can be expanded with more bits by adding resistors in a power-of-two sequence. Accurate output requires proper voltage matching from logic gates.
- 13.3: The R/2R DAC (Digital-to-Analog Converter)
- The R/2R DAC circuit is an alternative to the binary-weighted-input (R/2nR) DAC which uses fewer unique resistor values.
- 13.4: Flash ADC
- This page discusses the flash A/D converter, which uses comparators for high-speed signal conversion by comparing an input signal to various reference voltages. It has a significant drawback of requiring many components as output bits increase, needing 255 comparators for eight bits.
- 13.5: Digital Ramp ADC
- This page explains the operation of the stairstep-ramp or counter A/D converter, which involves a binary counter and a DAC that compares its output with an analog input signal. The counter counts upward until the DAC output exceeds the input voltage, at which point it stops and resets. The varying time intervals for updates based on the input voltage can result in slow sampling rates, making this method less efficient than other counter techniques in ADC applications.
- 13.6: Successive Approximation ADC
- This page discusses the advantages of the successive-approximation ADC over digital ramp ADCs. It explains how the successive-approximation register (SAR) efficiently counts bit values from the most to the least significant bit, using the comparator's output for rapid binary-analog matching. This method enhances speed by making larger adjustments, similar to decimal-to-binary conversion techniques.
- 13.7: Tracking ADC
- This page discusses an advanced counter-DAC-based converter using an up/down counter to track analog signals efficiently. It improves response times compared to traditional systems by eliminating the shift register. However, it faces challenges with binary output instability, referred to as "bit bobble." This can be mitigated by adding a shift register to latch output changes, enhancing stability and reliability in digital applications.
- 13.8: Slope (integrating) ADC
- This page explains single-slope and dual-slope analog-to-digital converters (ADCs). Single-slope ADCs convert analog signals using an integrator and a counter but suffer from calibration drift. Dual-slope ADCs improve accuracy by alternating integration between the input signal and a fixed reference, enhancing noise immunity and performance for high-accuracy applications.
- 13.9: Delta-Sigma ADC
- This page describes delta-sigma (ΔΣ) ADC technology, which converts analog signals to digital by integrating input voltage and comparing it using a 1-bit comparator, creating a feedback loop. This process generates a bitstream that represents the input signal, with higher negative inputs resulting in more "1's" in the output. Variations enable multiple stages and oversampling, improving resolution.
- 13.10: Practical Considerations of ADC Circuits
- This page covers essential aspects of Analog-to-Digital Converters (ADCs), emphasizing resolution and sample frequency. It defines resolution in binary bits and the limitations of a 10-bit ADC for detecting minute changes, as shown in a water tank example. The importance of sample frequency in accurately capturing quick analog signal changes is highlighted to prevent aliasing. Additionally, various ADC technologies are compared based on their resolution, speed, and step recovery capabilities.