Officials at Raytheon Co. of Lexington, Mass., and Texas Instruments Inc. (TI) of Dallas have signed a definitive agreement worth almost $3 billion authorizing Raytheon to acquire TI's defense electronics operations. The transaction will bring Raytheon's annualized defense electronics sales to $8 billion and its backlog to $9.3 billion. Raytheon will gain TI photonic technologies such as laser-guided weapons and night-vision systems.