Agilent 5991-3732EN Performing a Precision ADC Evaluation Using a Low Noise DC Source - Application Note c20 free download

File name 5991-3732EN Performing a Precision ADC Evaluation Using a Low Noise DC Source - Application Note c20

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