Good morning. I have a customer currently using the ADR421 as a voltage reference in multiple projects. The spec on this part indicates 1/F noise of 1.75uV and noise of 80nV/√Hz @1KHz. The noise graph shows that about same noise is present in the bandwidth of ~ 100Hz…10KHz.
The ADR441 appears to be a better, pin-compatible part with 1/F noise 1.2uV (~31% improvement versus ADR421) and noise of 48nV/√Hz @1KHz (40% improvement). My customer's bandwidth of interest is DC…80MHz.
1) Do you have noise graph data over the DC - 80MHz bandwidth for both the ADR421 and the ADR441 (Figure 27)? If so, can you please provide it to me?
2) Can you confirm that the noise graphs are obtained without the required 0.1uF capacitor on the output? My customer has a concern about an implicit low pass filtering effect given the ADR441 output impedance graph shown in Figure 31.
Richard A. Pensabene