** Philadelphia Semiconductor Index falls as much as 2.2%, last down 1.3%, and is set for second straight session of losses as higher yields weigh on the tech sector broadly .N
** Index closed at its highest since Nov. 7 on Monday, on hopes for AI-led demand after Microsoft's MSFT.O plan to invest $80 billion in AI-enabled data centers in 2025
** However, the index has retraced those gains and is now trading below the Jan. 3 close
** ON Semiconductor ON.O biggest index decliner, down 6.9%
** Advanced Micro Devices AMD.O declines 4.5% after HSBC Global Research downgrades the stock to "reduce" from "buy"
** Shares of AI chipmaker and index heavyweight Nvidia NVDA.O down 0.2% on the day after over 6% loss in prior session
** Smartphone chipmaker Qualcomm QCOM.O loses 1.4%, U.S.-listed shares of contract chipmaker Taiwan Semiconductor Manufacturing TSM.N and memory chipmaker Micron Technology MU.O down 2.1% and 2.3%, respectively
** Philadelphia Semiconductor Index .SOX has gained about 3.4% this month, after soaring over 19% in 2024
(Reporting by Lisa Mattackal)