Germanium transistors for operation above 1 KMC

Diffused base germanium transistors of two sizes have been designed for use as common base amplifiers above 1 Kmc. Both are coaxially encapsulated pnp structures in epitaxial germanium, with base layer widths of 0.3 microns. The smaller device has emitter and base stripes of 7.5 by 37.5 microns with 4 micron separation. A power output of 20 mw at 1 Kmc and 13 mw at 2 Kmc has been obtained with a bias power of 60 mw and an input drive of 2 mw. Insertion gain at 1 Kmc for the transistor with tuned input and output and no external feedback is 17 db with a reverse transfer through the device and tuning elements of -16 db. An amplifier with one transistor has provided 12 db of gain at a center frequency of 1.9 Kmc with a 3 db bandwidth of 200 Mc.