# Analog-to-digital converter

**ADCanalog to digital converteranalog-to-digital conversionanalog-to-digitalA/DADCsA/D converteranalogue-to-digital converterA/D convertersAD**

In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal.wikipedia

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### Effective number of bits

**effectivelyENOBreduced effective resolution**

The SNR of an ADC is often summarized in terms of its effective number of bits (ENOB), the number of bits of each measure it returns that are on average not noise.

Effective number of bits (ENOB) is a measure of the dynamic range of an analog-to-digital converter (ADC) and its associated circuitry.

### Aliasing

**aliasedaliastemporal aliasing**

The SNR of an ADC is influenced by many factors, including the resolution, linearity and accuracy (how well the quantization levels match the true analog signal), aliasing and jitter.

Audio signals are sampled (digitized) with an analog-to-digital converter, which produces a constant number of samples per second.

### Sampling (signal processing)

**sampling ratesamplingsample rate**

Furthermore, instead of continuously performing the conversion, an ADC does the conversion periodically, sampling the input, limiting the allowable bandwidth of the input signal.

In practice, the continuous signal is sampled using an analog-to-digital converter (ADC), a device with various physical limitations.

### Audio bit depth

**24-bitbit depthresolution**

The SNR of an ADC is influenced by many factors, including the resolution, linearity and accuracy (how well the quantization levels match the true analog signal), aliasing and jitter.

Quantization error introduced during analog-to-digital conversion (ADC) can be modeled as quantization noise.

### Digital signal (signal processing)

**digital signaldigitaldigital signals**

In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal.

The process of analog-to-digital conversion produces a digital signal.

### Jitter

**wanderphase jitterjitter buffer**

The SNR of an ADC is influenced by many factors, including the resolution, linearity and accuracy (how well the quantization levels match the true analog signal), aliasing and jitter.

If there is jitter present on the clock signal to the analog-to-digital converter or a digital-to-analog converter, the time between samples varies and instantaneous signal error arises.

### Oversampling

**oversampledoverachievingoversample**

The resolution determines the magnitude of the quantization error and therefore determines the maximum possible average signal-to-noise ratio for an ideal ADC without the use of oversampling.

In practice, oversampling is implemented in order to reduce cost and improve performance of an analog-to-digital converter (ADC) or digital-to-analog converter (DAC).

### Flash ADC

**Flash Analog to Digital Converterflash analog-to-digital converter**

A direct-conversion ADC or flash ADC has a bank of comparators sampling the input signal in parallel, each firing for their decoded voltage range.

A flash ADC (also known as a direct-conversion ADC) is a type of analog-to-digital converter that uses a linear voltage ladder with a comparator at each "rung" of the ladder to compare the input voltage to successive reference voltages.

### Quantization (signal processing)

**quantizationquantization errorquantized**

The resolution determines the magnitude of the quantization error and therefore determines the maximum possible average signal-to-noise ratio for an ideal ADC without the use of oversampling. The conversion involves quantization of the input, so it necessarily introduces a small amount of error or noise.

An analog-to-digital converter is an example of a quantizer.

### Digital filter

**filterdigitaldigital filters**

If a signal is sampled at a rate much higher than the Nyquist rate and then digitally filtered to limit it to the signal bandwidth there are the following advantages:

A digital filter system usually consists of an analog-to-digital converter (ADC) to sample the input signal, followed by a microprocessor and some peripheral components such as memory to store data and filter coefficients etc. Finally a digital-to-analog converter to complete the output stage.

### Sample and hold

**sample-and-holdS/Hsample-and-hold amplifiers**

Since a practical ADC cannot make an instantaneous conversion, the input value must necessarily be held constant during the time that the converter performs a conversion (called the conversion time). An input circuit called a sample and hold performs this task—in most cases by using a capacitor to store the analog voltage at the input, and using an electronic switch or gate to disconnect the capacitor from the input.

They are typically used in analog-to-digital converters to eliminate variations in input signal that can corrupt the conversion process.

### Digital-to-analog converter

**DACDACsdigital to analog converter**

A digital-to-analog converter (DAC) performs the reverse function; it converts a digital signal into an analog signal.

An analog-to-digital converter (ADC) performs the reverse function.

### Integral nonlinearity

Important parameters for linearity are integral nonlinearity and differential nonlinearity.

Integral nonlinearity (acronym INL) is a commonly used measure of performance in digital-to-analog (DAC) and analog-to-digital (ADC) converters.

### Successive approximation ADC

**successive approximationADCsSAR ADC**

A successive-approximation ADC uses a comparator to successively narrow a range that contains the input voltage.

A successive approximation ADC is a type of analog-to-digital converter that converts a continuous analog waveform into a discrete digital representation via a binary search through all possible quantization levels before finally converging upon a digital output for each conversion.

### Comparator

**voltage comparatorcomparatorsanalog comparator**

A direct-conversion ADC or flash ADC has a bank of comparators sampling the input signal in parallel, each firing for their decoded voltage range.

They are commonly used in devices that measure and digitize analog signals, such as analog-to-digital converters (ADCs), as well as relaxation oscillators.

### Signal-to-quantization-noise ratio

**signal-to-quantization noise ratio**

In an ideal ADC, where the quantization error is uniformly distributed between −1/2 LSB and +1/2 LSB, and the signal has a uniform distribution covering all quantization levels, the Signal-to-quantization-noise ratio (SQNR) is given by

The SQNR reflects the relationship between the maximum nominal signal strength and the quantization error (also known as quantization noise) introduced in the analog-to-digital conversion.

### Analog signal

**analoganalogueanalogue signal**

In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal.

Analog-to-digital converter

### Voltmeter

**Digital voltmetervolt metervoltmeters**

Converters of this type (or variations on the concept) are used in most digital voltmeters for their linearity and flexibility.

Analog voltmeters move a pointer across a scale in proportion to the voltage of the circuit; digital voltmeters give a numerical display of voltage by use of an analog to digital converter.

### Integrating ADC

**dual-slope analog to digital converterdual slope ADCsdual-slope**

An integrating ADC (also dual-slope or multi-slope ADC) applies the unknown input voltage to the input of an integrator and allows the voltage to ramp for a fixed time period (the run-up period).

An integrating ADC is a type of analog-to-digital converter that converts an unknown input voltage into a digital representation through the use of an integrator.

### Integrated circuit

**integrated circuitsmicrochipchip**

Due to the complexity and the need for precisely matched components, all but the most specialized ADCs are implemented as integrated circuits (ICs).

ICs can also combine analog and digital circuits on a single chip to create functions such as analog-to-digital converters and digital-to-analog converters.

### Spurious-free dynamic range

**SFDR**

In practice, the individual differences between the M ADCs degrade the overall performance reducing the spurious-free dynamic range (SFDR).

is also defined as a measure used to specify analog-to-digital and digital-to-analog converters (ADCs and DACs, respectively) and radio receivers.

### Delta-sigma modulation

**delta-sigmadelta-sigma modulateddelta-sigma modulator**

A digital filter (decimation filter) follows the ADC which reduces the sampling rate, filters off unwanted noise signal and increases the resolution of the output (sigma-delta modulation, also called delta-sigma modulation).

Delta-sigma (ΔΣ; or sigma-delta, ΣΔ) modulation is a method for encoding analog signals into digital signals as found in an analog-to-digital converter (ADC).

### Time stretch analog-to-digital converter

**time lensTime-stretchtime-stretch A/D conversion**

A time-stretch analog-to-digital converter (TS-ADC) digitizes a very wide bandwidth analog signal, that cannot be digitized by a conventional electronic ADC, by time-stretching the signal prior to digitization.

The time-stretch analog-to-digital converter (TS-ADC), also known as the time stretch enhanced recorder (TiSER), is an analog-to-digital converter (ADC) system that has the capability of digitizing very high bandwidth signals that cannot be captured by conventional electronic ADCs.

### Anti-aliasing filter

**anti-aliasinganti-aliasing (AA) filteroptical low-pass filter**

When sampling audio signals at 44.1 kHz, the anti-aliasing filter should have eliminated all frequencies above 22 kHz.

Anti-aliasing filters are commonly used at the input of digital signal processing system's analog to digital converter; similar filters are used as reconstruction filters at the output of such systems, for example in music players.

### Noise shaping

**noise-shapednoise shapernoise shapers**

In an oversampled system, noise shaping can be used to further increase SQNR by forcing more quantization error out of band.

Since around 1989, 1 bit delta-sigma modulators have been used in analog to digital converters.