While Fools should generally take the opinion of Wall Street with a grain of salt, it's not a bad idea to take a closer look at particularly stock-shaking upgrades and downgrades -- just in case their reasoning behind the call makes sense.

What: Shares of Microsemi (NASDAQ:MSCC) increased 2% today after Goldman Sachs upgraded the semiconductor solutions specialist from neutral to buy.

So what: Along with the upgrade, analyst James Covello planted a price target of $30 (from $26) on the stock, representing about 23% worth of upside to Friday's close. So while momentum traders might be turned off by Microsemi's year-to-date price sluggishness, Covello's call could reflect a sense on Wall Street that the company's turnaround prospects are becoming too cheap to pass up.

Now what: According to Goldman, Microsemi's risk/reward trade-off is rather attractive at this point. "While defense exposure has been a concern of ours, we believe Microsemi significantly undershipped end demand in 4QCY13 (its A&D sales were down 17% yoy), positioning it to benefit from improving orders (1QCY BTB above 1)," said Covello. When you couple that upbeat outlook with Microsemi's single-digit forward P/E, it's tough to disagree with Goldman's bullishness.