Requirements For Optimum Probe Performance - Keysight N7020A User Manual

2
Using the N7020A

Requirements for Optimum Probe Performance

Low Source Impedance Required
The N7020A is designed explicitly for measuring DC power supplies. In order to
maintain a flat frequency response across the probe's bandwidth, the DUT must
have extremely low source impedance, like that of a power rail. The N7020A has a
non-flat input impedance that transitions from 50 kΩ at DC to 50Ω at 1 MHz and
above. Therefore, if the DUT impedance is not low, it will divide with the probe's
impedance unequally across frequency, causing a non-flat measurement. The
recommended DUT impedance should be much less than 1 ohm. At 1 ohm, the
DC-to-AC non-flatness is about 2%.
impedances of 0Ω, 1Ω, 25Ω, and 50Ω.
Figure 5
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Frequency Response (Probe with N7022A Main Cable) Versus DUT Impedance
Figure 5 shows the non-flatness for DUT
N7020A User's Guide