In this article we examine the process of measuring a key performance characteristic, output impedance, using the Picotest J2130 DC Dias Injector and the OMICRON-Lab Bode 100 VNA.
There are many types of voltage references, including series references, shunt references and several that can perform as either series or parallel devices. The requirements vary greatly from application to application, though the general performance drivers remain the same. The general performance metrics include DC voltage accuracy, temperature coefficient, noise, output impedance, PSRR and stability.
The output impedance is of significant concern for high speed A/D converters, especially sigma-delta converters that see a capacitor charge at each clock event. The stability of the reference can be evaluated through the output impedance, and so that will be addressed in this application note. PSRR and reference noise, two other important parameters, will be addressed in separate article.