Comparison of 1/f PM noise in commercial amplifiers

In this paper we compare the 1/f phase modulation (PM) noise of two different families of commercial amplifiers under different operating conditions. The first family used GaAs heterojunction bipolar transistors (HBT) while the second used Si bipolar junction transistors (BJT) in a Darlington pair amplifier configuration. Three currents for the HBT family and four currents for the BST family were chosen for study. The PM noise of the amplifiers was measured at carrier frequencies of 5, 10, and 100 MHz. In general, the HBT-based amplifiers had somewhat lower PM noise than the BJT based amplifiers. Amplifiers operating with higher current generally had lower PM noise than those operating with lower current. A commercial feed-forward amplifier had much lower 1/f PM noise than all the other commercial amplifiers tested