ON Semiconductor announced Friday that it has received federal regulatory approval to complete its $2.4 billion purchase of local chipmaker Fairchild Semiconductor.

The Phoenix-based company had offered to buy Fairchild, which employs about 650 people locally, last December for $20 per share, but had to get numerous regulatory approvals before it could complete the acquisition.

If the deal closes, it is unclear what the sale will mean for the Fairchild plant in South Portland, where analog switches, USB devices, converters, speedy circuit breakers and other building blocks of digital circuitry are made. Some semiconductor analysts have said the sale could make the Maine operation vulnerable to closure because it is dated, while other industry observers say the cost to build a chip-making factory from scratch is prohibitively expensive, which supports the continuation of the Western Avenue facility.

According to a news release from the company, ON Semiconductor has accepted a consent order from the Federal Trade Commission to shed a line of business allowing it to acquire Fairchild. ON intends to sell an automotive ignition business, which generated less than $25 million in revenue during fiscal year 2015, to Littelfuse Inc. in Chicago to satisfy the FTC.

The deal still must be blessed by antitrust regulators in China, where Fairchild operates a plant in Suzhou.

“We need one more approval, and that is from China,” said Parag Agarwal, vice president of investor relations and corporate development for ON Semiconductor. “We are expecting that fairly soon.”

The deal was expected to be closed by the end of August and Agarwal said that timetable hasn’t changed.

CHANGING MARKETS

The products made in South Portland fall under the Analog Power Signal and Solutions division of the company. In Fairchild’s 2015 annual report, that particular segment of the company had lost revenue, going from $413.8 million in 2013 to $399.1 million in 2014, continuing its decline to $385.2 million last year. But of Fairchild’s three manufacturing divisions, the APSS had the smallest loss from 2014 to 2015, dropping 3.48 percent, while the other divisions – Standard Products and Switching Power Solutions – recorded losses of 5 and 4.6 percent, respectively.

The company reported revenue of $1.37 billion in 2015. Sales were down 4 percent over 2014, according to Fairchild’s annual report.

When ON Semiconductor announced its intent to buy Fairchild, Keith Jackson, ON’s president and chief executive officer, said the overlap between the two companies was “minimal” and that the product lines would complement each other.

“Even though the two companies have complementary product portfolios, they serve similar end markets and a similar set of customers in similar geographies,” Jackson said in an interview with the Portland Press Herald. “There is a lot of commonality between the manufacturing and logistics operations of the two companies.”

ON Semiconductor said it expects to save about $150 million a year once the sale is completed. About $30 million will come from better coordination of supply chains, Bernard Gutmann, ON Semiconductor’s executive vice president and chief financial officer, said in an interview last winter. He also said the combined company could save on general expenses, and that many of the two companies’ research and development functions will be redundant under single ownership.

The FTC insisted that ON Semiconductor dispose of the automotive ignition business because a merger with Fairchild would mean the combined company would control 60 percent of the world’s market and “it is likely that the proposed merger would substantially lessen competition in the worldwide market for Ignition IGBTs, resulting in higher prices and reduced innovation,” according to the FTC order. IGBT stands for insulated gate bipolar transistor.

Deals involving chip makers have been increasing globally because the costs for designing chips are rising and sales are slowing. Buying companies that already make chips and have a piece of the market, instead of investing in new designs and building new plants, is seen as the preferred way for a company to expand its market.

According to The New York Times, there were 10 attempts by Chinese semiconductor companies to buy competitors in the year prior to the ON Semiconductor offer. In January, Fairchild considered a higher bid of $22 per share from a Chinese consortium, but rejected it because it didn’t think the deal could clear antitrust hurdles.

Estimated at $1.3 trillion, the semiconductor market is dominated by China, which is the top fabricator and biggest producer of consumer goods using chips.

Fairchild has been ramping up its operations in China. Last year, 43 percent of its revenue, or $590 million, was generated in China. That compares with 39 percent of revenues in 2014 and 36 percent in 2013.

Of the $1.37 billion in revenue recorded in 2015, only 9 percent was generated from U.S. sources ($123.3 million). Europe accounted for 16 percent; Taiwan accounted for 9 percent; South Korea, 6 percent; other Pacific nations accounted for 16 percent.

Stephan Ohr, a semiconductor analyst for Gartner, a high-tech research and advisory firm, said at the time of ON’s offer that the South Portland plant wasn’t known for being an industry innovator and that its facilities were older than most of the plants already in ON’s network. Conversely, Betsy Van Hees, an analyst for Wedbush who specializes in the semiconductor industry, said the cost to build new semiconductor plants is prohibitive, which is fueling merger and acquisition activity worldwide. She said it was unlikely the South Portland plant would be closed, although there could be some layoffs of redundant positions in the ON acquisition.

News of the FTC approval did little to affect Fairchild’s stock price, which closed the week at $19.90, little changed from its opening price on Monday of $19.80. ON Semiconductor stocks, however, got a boost from the news. Its stock price opened the week at $10.25 per share and closed at $11.03.

Fairchild was headquartered in South Portland until 2011, when it moved to San Jose, California. It still operates administrative offices on Running Hill Road in South Portland, not far from its production plant.