In　order　to　improve　the　thermal　stability　of　RF　power　HBT　and　eliminate　the　self-heating　effect　which　degenerates　the　transistor＇s　electrical　characteristics,　the　physical　significance　of　thermal　stability　factor　S　is　presented　in　detail　based　on　the　thermal-electric　feedback　network　analysis.　Furthermore,　the　expression　of　the　minimum　ballasting　resistance　RC　of　HBT　to　compensate　the　self-heating　effect　(S=0)　is　presented　by　taking　into　account　of　the　temperature　dependence　of　emitter　current,　the　valence-band　discontinuity　at　emitter　junction　(ΔEv),　the　bandgap　narrowing　due　to　heavy　doping　(ΔEg),　additional　ballasting　resistance　in　emitter　and　base.　It　is　found　that　the　higher　the　temperature　T　is,　the　smaller　the　minimum　ballasting　resistance　RC　to　compensate　the　self-heating　effect　is　under　the　condition　that　(ΔEv+ΔEg)＞2KT.　Owing　to　the　reducing　of　ballasting　resistance,　RF　power　HBT　will　provide　higher　output　power,　power　gain,　and　power-added　efficiency　(PAE)　in　an　amplifier　block.