In the design of microwave bipolar transistors, there has been extensive utilization of three basic geometries: interdigitated, overlay and mesh emitter. In view of the obvious cost-performance-reliability trade-offs of the geometrical designs, an understanding of attenuation along un-metallized stripes is imperative. This paper summarizes an experimental and theoretical investigation of the variation of output power by the r.f. attenuation along a diffused stripe where current was fed from one end only. The experiments have employed the overlay geometry with 2.5 µm linewidths and 4 µm spaces. Diffused stripe length, L
e, was varied while the emitter periphery, P
e, the base area, A
b, and the emitter area, A
ewere kept constant. At a frequency of 1 GHz, it was observed that for the same input power, the output power decreased by

in Class C operation and

in Class A as L
ewas increased from 19 µm to 36 µm. Interestingly, in both modes of operation, no change in output power was noted for L
e\´s between 12 µm and 19 µm. The obvious implication is that in these structures r.f. attenuation does not play a dominant role until the stripes reach a length of ∼ 20 µm, allowing the use of quite wide emitter metallization. A simple analysis has been carried out to better understand the r.f. attenuation mechanism and relate it to experimental data. The attenuation constant,

, was calculated using ordinary transmission line theory. Then, the collector current, I
e, was found employing this value of

. Variation of the output power was, then, inferred from the variation of I
e2. Correlation between theory and experiment is satisfactory considering the simplifications introduced into the analysis.