$1.39 billion from Tsinghua Holdings Co. Ltd.
The Chinese company said Tsinghua outlined in a letter dated Thursday an offer that amounts to $28.50 in cash for each American depositary share. That represents a premium of 20 percent over Wednesday's closing price of $23.73 for the U.S.-traded shares. The company had about 48.7 million American depositary shares outstanding at the end of the first quarter.
Tsinghua Holdings is a state-owned corporation funded by China's Tsinghua University.
Spreadtrum shares climbed 23 percent, or $5.16, to $27.45 before markets opened.
The company's stock also jumped earlier this month after Spreadtrum hiked its second-quarter revenue expectations well beyond analyst forecasts. The company had said it was raising its expectations in part because of strong demand for low-cost smartphones.
Spreadtrum shares had already climbed more than 26 percent, as of Thursday, since closing 2012 at $17.62.