Evaluation of High-Voltage Bias-Tee for Capacitor Characterization under DC Bias

The voltage dependence of capacitors is important for various applications such as EMC filters and DC link structures in power electronics, as it can significantly affect the device behavior. Understanding capacitance variation over wide bias ranges, including up to kilovolt levels, is of particular interest and has been the subject of numerous academic studies. As these academic studies use self-built bias structures (bias tees) for high voltage and/or high current DC biasing during impedance measurements, replicating such setups is often challenging. This study presents the application of a commercially available 1000V bias tee for capacitance extraction using a vector network analyzer. Necessary procedures, such as setup calibration, are described in detail and the accuracy of the approach is analyzed. A Ceralink ceramic capacitor is used as the device under test and a voltage-independent thin film capacitor as reference.