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 power-control chip designer Monolithic Power Systems (Nasdaq: MPWR) powered their way to 15.5% gains today amid heavy trading and remain poised right at the intraday high-water mark.

So what: Monolithic thoroughly shocked the Street with $0.13 of non-GAAP earnings per share on $44.5 million in sales. Monolithic shares have come back from a deep trough in March to set new six-month highs.

Now what: Monolithic Power Systems is like a box of chocolates -- you never know what you're gonna get. This quarter and the last were both terrific surprises worthy of investor optimism, but the company had nothing good to say two quarters ago. If you're losing sleep over these mood swings, you might be better off investing in direct rival and industry giant Texas Instruments (NYSE: TXN), or in Micrel (Nasdaq: MCRL) if you're looking for a small-cap performer in this sector that doesn't make you reach for the Tums on a regular basis.

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Fool contributor Anders Bylund holds no position in any of the companies discussed here. The Fool owns shares of Texas Instruments. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool is investors writing for investors.