TradingKey – On September 28, Eastern Time, Nvidia (NVDA) shares bucked the trend to rise amid broader pressure on tech stocks, with its newly announced mega stock buyback plan serving as the main catalyst. On September 28, Nvidia announced that its board of directors approved an additional $150 billion for its share repurchase authorization, raising the remaining executable amount to $235 billion, which it plans to execute before the end of fiscal year 2028, setting a record for the largest buyback authorization in U.S. stock market history. Following the announcement, Nvidia rose 1.68% that day to $228.86, touching an intraday high of $233.21, while the Nasdaq Index fell 0.92% during the same period, indicating that the buyback news…