The software add-on allows the instrument to perform non-invasive stability margin (“NISM”) measurement. NISM is an alternative to a Bode plot measurement that allows the user to test circuit or filter stability even when the control loop is not accessible. It determines phase margin from an output impedance measurement via group delay. This capability, available for several other VNA instruments (including OMICRON Lab’s Bode 100 and Keysight’s E5061B and E5071C), allows the user to measure the stability of op amps, voltage references, voltage regulators, LDOs, switching amplifiers, POLs, input filters and all types of power converters through their output impedance.
The software guides the user through a few simple steps to obtain the stability margin from a circuit’s output impedance. The measurement results can be saved or printed as with other ZNL measurements.
ZNL users can use one, two, and three port impedance measurements which the software can convert to phase margin. The software supports the full frequency range of the instrument to assess the stability of all types of the aforementioned circuits. Options add Picotest’s 1 and 2 port PDN transmission line probes which greatly ease the measurement of output impedance due to their small form factor and minimal circuit loading (< 0.2pf).