HGM221S30V220 Gradient Impedance Matching MOS Capacitor — 220 pF 30V Ultra-Wideband In short: The HGM221S30V220 is a 220 pF, 30 V single-layer MOS capacitor built on high-resistivity float-zone silicon with a thermally grown SiO2 dielectric. Its gradient impedance interface smooths the transition to the surrounding circuit so the capacitor keeps a consistent response over an ultra-wideband range, and it also holds sub-degree phase consistency between elements for array use.