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

What: Shares of chip maker RF Micro Devices (Nasdaq: RFMD) plummeted 20% on Friday after the company lowered its third-quarter revenue guidance.

So what: RF Micro's cut was so big -- the company now sees quarterly revenue of $225 million versus its prior forecast of $250 million -- that analysts are being prompted to lower their valuation estimates yet again. The stock has been crushed over the past year on European demand concerns, but management cited a sharp drop in Chinese 2G orders as the main culprit this time, triggering a fresh new set of fears among investors.

Now what: I'd look into this pullback as a possible entry point. "Despite this challenging macro environment, [RF Micro] is winning new business," CEO Bob Bruggeworth said, "and we fully expect to grow in fiscal 2013, supported by market share gains, new product launches, and expanding relationships with both channel partners and customers." Best of all, with the stock now down 32% over the past three months alone and sporting a cheapish forward P/E of 7.8, that long-term optimism doesn't exactly come at a premium.

Interested in more info on RF Micro? Add it to your watchlist.