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Keysight Technologies
Performing a Precision ADC
Evaluation Using a Low Noise
DC Source
Application Note
Featuring the Keysight B2961A/
B2962A 6.5 Digit Low Noise
Power Source
Introduction
As the operating voltages of analog-to-digital converters (ADCs) continue to
decrease, the voltage step associated with the least significant bit (LSB) also
decreases. If the voltage step of the LSB becomes smaller than the ADC's
equivalent input noise, then a stable and low-noise test signal is essential for
precise ADC evaluation. In these situations, a conventional DC power supply
cannot be used to evaluate precision ADCs because its noise level is too high
compared to the LSB step size. A solution for making these types of measure-
ments is to use a dual-channel low noise power source, such as the Keysight
Tecnologies, Inc. B2961A or B2962A 6.5 digit low noise power source.
This application note outlines the importance of, and the requirements for,
low-noise DC signal sources for ADC evaluation, and explains why the
Keysight B2961A/62A is the well-suited for this application.
Key Terms Ultra-Low Noise Filter Performance
There are three key terms
used throughout this
application note. In the The noise density of the B2961A or B2962A when used with the N1294A-021
context of this paper, their ultra low noise filter (ULNF) is 1 nVrms/Hz at 10 kHz. For a 20 MHz bandwidth
definitions are as follows: this corresponds to a noise level of less than 10 Vrms (about 60 Vp-p noise).
This is lower than the LSB voltage of most high-speed, 14-bit ADCs, allowing the