what does 3dB bandwidth means for ADC input

[syedshan]

hello every one,


I am using AD62P49 ADC. In the ADC data sheet I come accross the following statement and I cannot actually understand what it exactly mean here by 3 dB bandwidth and then what does it mean by HIGH 3-dB bandwidth.

The input sampling circuit has a high 3-dB bandwidth that extends up to 700 MHz (measured from the input pins to the sampled voltage).

Thans

 

[FvM]

The term "HIGH 3-dB bandwidth" isn't used in the datasheet as far as I'm aware of. I assume, you're confused that ADC behaviour for frequencies above the Nyquist rate is specified?

It's particularly interesting in undersampling applications, for a brief overview see: https://en.wikipedia.org/wiki/Undersampling

 

[crutschow]

I believe it's referring to the -3dB high frequency response point for the input circuitry prior to the sampling circuitry.

 

[FvM]

It's not only the bandwidth of the input circuitry prior to the sampling circuitry, it's essentially determined by the aperture time, the width of the sampling window.

 

[mpig09]

Hi FvM:

Does it mean the bandwidth of the sampled circuit ?

If I have any mistake, please correct me.
mpig

 

[FvM]

Yes, bandwidth of the sampling circuit.

 

[zorro]

I am using AD62P49 ADC. In the ADC data sheet I come accross the following statement and I cannot actually understand what it exactly mean here by 3 dB bandwidth and then what does it mean by HIGH 3-dB bandwidth.

I think it is a drafting error or misuse of the term; the correct term should be "WIDE bandwidth".
"High bandwidth" and "low bandwidth" appear several times in the data sheet where "wide" and "narrow" would fit better.
Regards

Z