Impact of Layout Parasitics and Thermal Coupling on PA performance and ruggedness in SiGe HBTs

In this paper, we present the impact of layout parasitics and thermal coupling on a SiGe PA power cell using the Globalfoundries 4
^th
generation 350nm SiGe Power Amplifier technology. Device sizes varying from a unit cell (120μm
²
) to PA array (720μm
²
and 1440μm
²
) is used to compare DC, AC, and large signal performance. Measured and simulated data shows that the layout of power cell can be optimized to reduce wiring parasitic non-uniformity and thermal heat dissipation to improve the large signal power performance and ruggedness. It is found that layout style A is better and can give 8% better PAE, 0.5dB better Gain and 20C lower peak delta-temperature (∆T).