A 5 watt, 500 Mc transistor

Abstract

A new high performance transistor has been developed which gives 5 watts of output power at 500 Mc with more than 6 db gain in a Class C amplifier circuit. This transistor makes use of a new geometry which substantially increases the ratio of emitter edge to emitter area, achieving a ratio of 8 mils of edge/square mil of emitter area. This improved geometry makes possible a substantial extension of the high-frequency output power capability of transistors. For this large area unit f max is in excess of 1 KMC, BV CEO(sua) greater than 90 volts, and dissipation capability in excess of 15 watts. The new geometry makes use of a large array of separate emitter elements, 144 in all, each of which is small enough to achieve a high periphery to area ratio. The interconnection of the emitter-base structure makes use of both metallic and semiconductor regions to spread the current flow suitably. Design considerations relating to transit and charging times and to the specific choices of resistivities and device configuration will be described. A new package structure will be described which combines the advantages of BeO collector isolation, good thermal resistance (10°C/watt), and low parasitic reactances. The critical aspects of photoresist techniques will be elaborated upon. Performance data at 500 Mc in a 5 watt amplifier will be described. An oscillator circuit capable of delivering 1.5 watts of output power with 30% conversion efficiency at 800 Mc will be shown.