On the large-signal robustness of SiGe HBT LNAs for high-frequency wireless applications

We present measured results and analysis from high-power testing of three different X-band SiGe HBT LNAs. The custom measurement setup allowed high RF power (up to 32 dBm) to be applied to the input of the LNAs for 400 sec. During the stressing, the bias current was monitored and the pre/post-stress dc and ac characteristics were measured. The results indicate that, in the three LNAs tested, catastrophic failures can occur at these high powers, while at lower input power (less than 30 dBm), the LNA gain is degraded. Analysis shows that during the stressing, the collector current density inside the transistors increases enough to damage the device, in a manner similar to that experienced during mixed-mode reliability stress.