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 semiconductor manufacturer ON Semiconductor (Nasdaq: ONNN) were flashing green today, gaining as much as 11% in intraday trading on a heady day for the semiconductor sector.

So what: ON Semiconductor investors can give a big "thank you" to Linear Technology (Nasdaq: LLTC) today. While Linear's fiscal-second-quarter just managed to deliver in-line results, the company guided to better-than-expected results for the upcoming quarter. That optimistic assessment got investors fired up about the entire industry, boosting not only Linear, but also ON, Atmel (Nasdaq: ATML) (up 7.9% at this writing), TriQuint (Nasdaq: TQNT) (up 6%), Altera (Nasdaq: ALTR) (up 9.8%), and quite a few others.

Now what: Is it automatically true that what's good for Linear is good for the rest of the semiconductor group? Not necessarily. If Linear is getting its optimistic forecast from expectations that it will be eating the lunch of other semiconductor companies, that's only good news for Linear.

More likely, though, the optimism of Linear may be showing glimmers of pickup in the semi space. With that in mind, some excitement from investors seems reasonable today; I'm just wondering whether the big stock jumps throughout the sector may be overly exuberant.

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