A germanium ultra high speed switching transistor

A mesa type germanium switching transistor, designed for switching rates up to 100 mc per second in a saturating circuit, has been developed. It features a unity-gain frequency of 1.5 to 4 Kmc, collector and emitter depletion capacitance of 1 pf each, and operation at a collector current of up to 50 ma. Switching times in a special saturated switching circuit have been measured as low as 5 Nsec total. The current gain at a collector current of 50 ma is typically 30 or higher and collector breakdown voltage is 10 Volts or higher. Epitaxial pp⁺material is used, resulting in low collector saturation voltage (.5 volts at 50 ma) and low storage time. The epitaxial structure also results in a relatively constant fTup to a collector current of 50 ma, making the transistor suitable for high current switching.