Eight hundred MHz high-efficiency MIC power amplifier

Two and three-stage, high-efficiency MIC power amplifiers have been constructed with a lumped element circuit in the 800MHz band. Each amplifier is formed on a beryllia substrate, of 20mm × 20mm × 2mm and 20mm × 25mm × 2mm for two-stage and three-stage respectively. The transistor chips are bonded on a beryllia substrate directly without packaging, and operated as common emitter class C amplifiers. The amplifiers have been constructed with no adjustment using the same circuit constants successfully. And almost the same characteristics have been obtained with high yield. For the two-stage amplifier, power gain could deliver, 17dB and around 45% of the total efficiency could be obtained, in the 800MHz frequency band, when operated at 13V and input power of 200mW. Further for the three-stage amplifier, output power gain of 23dB and the total efficiency of 40% was obtained in this frequency band when operated at 13V and input power of 40mW. These amplifiers release heat well because of sufficient heat spreading structure. The thermal resistance of the third-stage transistor is less than 3.5°C/W when the case temperature is 150°C.