Abstract: For a grid-controlled electron source to operate at extremely high frequencies, as in planar triodes, the control grid must be situated very close to the emissive cathode. Mechanical and thermal distortions have put minimum limits on grid spacings and hence on the maximum operating frequency of grid-controlled tubes. To overcome these limits the grid structure is formed as a network of web members which are part of a laminated sheet having metal layers bonded to opposite surfaces of an insulating layer. One metal layer is affixed to the emissive surface of a metallic matrix cathode and the other metal layer forms the control grid.