Bipolar Microwave Linear Power Transistor Design

Design considerations for n-p-n bipolar microwave linear power transistors are discussed. Optimization procedures are presented for determining emitter width for a specfic operation frequency, emitter ballasting resistance, and active area geometry based on calculated temperature distributions. A transistor chip designed for 4-GHz operations using these procedures achieved a linear power output of 27.5 dBm at a 1-dB compressed gain of 7 dB with a power added efficiency of 23 percent. Junction temperature rise was limited to 90°C.