High speed analog to digital converter

High speed analog to digital converter: A Low Latency 4-bit High Speed Analog to Digital Converter

Conversion of analog signals into its digital representation is needed everywhere in the electronics world. The analog signals can be created in many different ways, for example, produced by sound into a microphone or light entering a camera etc.

The main basic metrics that define an ADC are its sampling speed, number of bits or resolution (within the specified input signal amplitude range), and analog input bandwidth. The sampling speed defines how many digital copies of the analog signal are taken in a particular time period. It’s usual to express the sampling speed in terms of HZ, so in this case the time period is 1.0 second. High speed analog to digital converters at present day usually entails that these ADCs are working at sampling speed over 1.0GHz.

The resolution refers to how many discrete values the ADC can produce over the amplitude range of the input analog signal. A 1.0 bit ADC would just be a binary decision circuit (0 or 1) while ADCs can have resolution over +20 bits.

Finally, the input bandwidth of an ADC places a limit on the frequency of the input analog signal that can be properly digitized. It’s common practice to have ADCs function at the Nyquist rate so the sampling rate should be twice the input bandwidth. For example, a high speed analog to digital converter with a 1.0GHz input bandwidth should have a 2.0GHz sampling rate (i.e. 2.0Gsamples/s or 2.0GS/s).

In general, ADCs with a high number of bits have lower input bandwidths and sampling rates. On the other end of the spectrum, ADCs with a low number of bits have higher input bandwidths and sampling rates.

ADSANTEC Inc. offers an up to 16GS/s 4-bit Flash ADC with 20GHz of input analog bandwidth. It’s an under sampling device since it can’t sample at 40GS/s, the Nyquist rate for a 20GHz input bandwidth. The company offers two main ADC versions: one outputs bits at full rate (4 channels at 16Gb/s) while the other outputs a demultiplexed version of the output bits (16 channels at 4Gb/s). Other key included functionality is a built in PRBS generator for downstream channel alignment.

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