In other articles, I have outlined the reasons why I think the semiconductor industry is poised for strong stock performance and why I think MEMC Electronic Materials (MEMC) is the best play on the sector.

But I also realize that a bullish semiconductor outlook right now involves making a grab at that falling knife. Therefore, I thought I should also let people know which semiconductor stock looks most vulnerable to a downturn.

I think that stock is Microsemi (MSCC).

Microsemi is a leading designer, manufacturer and marketer of high performance analog and mixed-signal integrated circuits and high-reliability semiconductors. Its products manage and control or regulate power, protect against transient voltage spikes and transmit, receive and amplify signals.

Microsemi has held up fairly well, handily beating the performance of the Semiconductor HOLDRs (SMH) over the last year. This may be due largely to its strong end markets, which include defense, commercial aerospace, industrial/semicap, medical, mobile connectivity and notebooks, monitors and LCD televisions.

More Questions Than Answers

To me, however, the strong end markets only raise questions concerning Microsemi’s fundamental performance. For example, with such strong end markets, why did its cash from operations fall by more than half in the year ended September 30, 2007, compared with the prior year? Why is its inventory rising faster than sales, and why is its gross margin slipping?

I turned to the company’s latest 10K in hope of finding answers.

To begin with, the area is highly competitive. According to the 10K (emphasis added), “some of our current major competitors are Freescale Semiconductor, Inc., National Semiconductor Corp. (NSM), Texas Instruments, Inc. (TXN - Annual Report), Koninklijke Philips Electronics (PHG), ON Semiconductor Corp. (ONNN), Fairchild Semiconductor International, Inc. (FCS), Micrel Incorporated (MCRL), International Rectifier Corp. (IRF), Semtech Corp. (SMTC), Linear Technology Corp. (LLTC), Maxim Integrated Products, Inc. (MXIM), Skyworks Solutions, Inc. (SWKS), Diodes, Inc. (DIOD), Vishay Intertechnology, Inc. (VSH), O2Micro International, Ltd. (OIIM) and Monolithic Power Systems, Inc.