The　influence　of　various　geometry　sizes　of　SiGe　HBTs　on　noise　performance　of　the　monolithic　low　noise　amplifier(LNA)　is　investigated　in　this　paper.　Four　types　of　LNAs　using　SiGe　HBTs　with　different　geometry　parameters　are　fabricated　in　a　0.35　μm　SiGe　BiCMOS　process　technology.　The　measurement　data　indicates　that　at　a　given　bias　condition,　a　smaller　emitter　width　slightly　improves　the　noise　figure(NF)　if　the　ratio　of　emitter　width　to　emitter　length　is　small,　however　a　proper　longer　emitter　width　and　less　emitter　strips　can　significantly　improve　the　overall　NF　without　significant　the　gain　degradation.　Geometry　scaling　data　show　that　the　optimal　LNA　using　SiGe　HBT　with　AE=4　μm×40　μm×4　has　the　minimum　NF　of　2.6　dB,　the　maximum　associated　gain　of　27.4　dB　and　the　optimum　noise　source　resistance　of　nearly　50　Ω　over　0.2-1.2　GHz　compared　to　other　device　geometries.　The　die　areas　are　only　0.2　mm2　due　to　the　absence　of　inductors.