UK technology firm ARM Holdings is to be bought by Japan's Softbank for £24bn ($32bn) it confirmed on Monday.
The board of ARM is expected to recommend shareholders accept the offer - which is around a 43% premium on its closing market value of £16.8bn on Friday.
The Cambridge-based firm designs microchips used in most smartphones, including Apple's and Samsung's.
ARM, which was founded in 1990, employs more than 3,000 people.
Shares in the UK technology firm surged by 45% at the open of the London Stock Exchange to 1,742.85p per share, adding £7.56bn to ARM's market value.
ARM said it would keep its headquarters in Cambridge and that it would at least double the number of its staff over the next five years.
The deal will be funded by Softbank's own cash reserves and a long term loan from Japan's Mizuho Bank.
Softbank is one of the world's biggest technology companies and is run by its founder, Japanese entrepreneur Masayoshi Son.
It has previously acquired Vodafone's Japanese operations and the US telecoms company Sprint. The $20bn deal was the biggest foreign acquisition by a Japanese firm at the time.
Softbank intends to preserve the UK tech firm's organisation, including its existing senior management structure and partnership-based business model, ARM said.