Semtech Corp.’s fiscal first-quarter net income plunged 90 percent as the specialty semiconductor maker took charges related to the largest acquisition in its history. But shares rose in after-hours trading Thursday after company provided slightly better-than-expected guidance for the current quarter.

After the Thursday markets closed, the Camarillo maker of chips used in power-management devices and automated test equipment reported net income of $2.2 million (3 cents a share) for the quarter ended April 29, compared with $22.6 million (34 cents) in same period a year earlier. Net revenue fell 4.7 percent to less than $117 million.

Excluding one-time items, net income 27 cents a share. Analysts surveyed by Thomson Reuters on average expected the company to report adjusted net income of 31 cents on revenue of nearly $120 million.

Semtech in March completed its $494 million acquisition of Canadian chipmaker Gennum Corp. Results in quarter were affected by a purchase accounting adjustment of $12.9 million and expenses of $18.6 million related to the acquisition. In addition, operating expenses rose 57 percent to $74.5 million.

“We not only closed and financed the largest acquisition in company history, we also saw a return to growth in bookings in all end markets and solid design win activity,” said Chief Executive Mohan Maheswaran in a statement. “The ongoing strength in our organic business, combined with the opportunity to expand into new markets with the addition of Gennum, gives us confidence that fiscal year 2013 will be another exciting year for Semtech.”

Looking ahead, Semtech expects to report fiscal second-quarter adjusted net income of 37 to 45 cents a share, with net sales in the range of $146 million to $154 million. The Wall Street consensus is for adjusted net income 41 cents on revenue of $149 million.

Shares earlier closed down 7 cents, or 2.9 percent, to $23.70, and rose nearly 3 percent in after-hours trading.