Electronic devices such as cellular telephones may include wireless communications circuitry such as power amplifiers. Power amplifiers, transmission lines, and other circuit associated the power amplifiers may generate different amounts of heat depending on their operating frequency. High-heat-producing power amplifiers may be biased at lower bias voltages than low-heat-producing amplifiers to equalize temperatures and enhance performance. Performance may also be optimized by placing power amplifiers on a printed circuit board so that the high band amplifiers are placed in regions that can dissipate more heat, whereas low band amplifiers are placed in regions that dissipate less heat.