Why iRobot, TriQuint Semiconductor, and Harmony Gold Soared Today

Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

Economic woes have plagued the markets in 2014, but today, the stage belonged to Janet Yellen, and the Federal Reserve chair delivered an impressive opening performance. Major stock market benchmarks were up more than 1% Tuesday, but that paled in comparison to the larger gains that iRobot , TriQuint Semiconductor , and Harmony Gold enjoyed today.

iRobot jumped 11% after the robotic electronics maker's intellectual-property law firm announced that it had been ranked No. 5 on a list of top patent portfolios in the electronics and instruments industry. With even higher showings in the "science strength" and "industry impact" categories, iRobot has developed technology that has had an impact not just on its own products but on the entire industry's offerings as well. Moreover, as Google bought Boston Dynamics and other robot-making companies recently, interest in iRobot as a potential takeover candidate has increased as well.

TriQuint also gained 11% as the company reportedly turned to Wall Street giant Goldman Sachs for assistance in fending off unwanted pressure from activist investors at Starboard Value. With the hedge fund pushing for aggressive moves like selling off its power-amplifier business or divesting its in-house manufacturing capability in favor of third-party foundry services, TriQuint likely wants to assess all of its available options. Yet with Starboard having announced its intention to begin a proxy battle to name directors to TriQuint's board at its annual meeting later this year, TriQuint needs to act carefully but firmly in order to fulfill its obligations to its shareholders.

Harmony Gold rose 9% on a strong day for gold, which reacted favorably to Dr. Yellen's testimony as well. Most gold-mining stocks posted solid gains Tuesday, but Harmony in particular jumped because its relatively high production costs leave it less margin than lower-cost miners. As a result, when gold rises, it has a more dramatic impact on potential future profits for Harmony than with other mining companies. It's unclear whether gold's gains will continue, but signs of Fed accommodation continuing are generally a positive for the market.