A 900 MHz 100 W CW mesh emitter type transistor with P.H.S. structure

A Mesh Emitter type silicon bipolar transistor that can deliver 120 watts cw output power at 900 MHz from a single chip with P.H.S.(Plated Heat Sink ) structure has been developed. The transistor pattern and the P.H.S. structure were optimized to obtain the lowest thermal resistance from a single chip. A developed 4.75 mm long and 1.5 mm wide single transistor chip consists of 36 cells of which the total emitter periphery is 390 mm. In order to reduce the thermal resistance, the silicon substrate was thinned to 25 um thickness, and 25 um thick silver and gold plated multi-layers were applied as the heat sink. The resulting packaged transistor with an input internal matching network delivered 120 watts cw output power with 8.8 dB gain and 55% collector efficiency at 900 MHz and 50 V collector supply voltage common base operation.