![]() Noise shaping: moving noise to higher frequencies above the signal of interest, so they can be easily removed with low-pass filtering.Higher linearity afforded by low-bit DACs (for instance, a 1-bit DAC that only outputs two values of a high voltage and a low voltage is perfectly linear, in principle).Higher accuracy in time (afforded by high-speed digital circuits and highly accurate clocks).This can achieve comparable quality by taking advantage of: Oversampling converters instead produce a lower-bitdepth result at a much higher sampling frequency. Higher-bit methods seek accuracy in amplitude directly, but require extremely precise components and so may suffer from poor linearity. In a conventional ADC, an analog signal is sampled at a relatively low sampling frequency near twice the signal's highest frequency and quantized by a multi-level quantizer to produce a multi-bit digital signal. Digitizing it enables noise-free transmission, storage, and processing. When transmitting an analog signal directly, all noise in the system and transmission is added to the analog signal, reducing its quality. The coarsely-quantized output of a delta-sigma ADC is occasionally used directly in signal processing or as a representation for signal storage (e.g., Super Audio CD stores the raw output of a 1-bit delta-sigma modulator). Primarily because of its cost efficiency and reduced circuit complexity, this technique has found increasing use in modern electronic components such as DACs, ADCs, frequency synthesizers, switched-mode power supplies and motor controllers. In both cases, the temporary use of a lower-resolution signal simplifies circuit design and improves efficiency. A delta-sigma DAC encodes a high-resolution digital input signal into a lower-resolution but higher sample-frequency signal that is mapped to voltages, and then smoothed with an analog filter. A delta-sigma ADC first encodes an analog signal using high-frequency delta-sigma modulation and then applies a digital filter to form a higher-resolution but lower sample-frequency digital output. Subsequent low-pass filtering easily removes this high frequency noise and time averages the signal to achieve high accuracy in amplitude.īoth ADCs and DACs can employ delta-sigma modulation. It achieves high quality by utilizing a negative feedback loop during quantization that continuously corrects quantization errors and moves quantization noise to higher frequencies well above the signal's frequency range. It is also used to convert high- bitdepth digital signals into low-bit, high-frequency digital signals as part of the process to convert digital signals into analog as part of a digital-to-analog converter (DAC). Delta-sigma ( ΔΣ or sigma-delta, ΣΔ) modulation is an oversampling method for encoding analog signals into digital signals as found in an analog-to-digital converter (ADC).
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