(Reuters) - Macquarie Equities Research downgraded shares of Texas Instruments Inc (>> Texas Instruments Incorporated), Altera Corp (>> Altera Corporation) and Xilinx Inc (>> Xilinx, Inc.) and cut its rating on the U.S. semiconductor sector to "neutral," citing stretched valuations and growing capacity.

"Consensus estimates for our group are already assuming better-than-normal revenue growth throughout 2012 as the cyclical recovery has become broadly accepted," Macquarie analyst Shawn Webster said.

Webster ? who had been relatively positive on U.S. semiconductor stocks over the last one and a half years ? downgraded the sector and said valuations are now slightly stretched and consensus forecasts are no longer conservative.

Macquarie downgraded Texas Instruments Inc (>> Texas Instruments Incorporated) to "neutral" from "outperform," saying the company's earnings power may be limited by the absence of organic share gains.

The brokerage also cut its rating on Altera Corp (>> Altera Corporation) and Xilinx Inc (>> Xilinx, Inc.) to "neutral," citing limited evidence of superior growth potential for programmable logic chips.

Macquarie, however, upgraded Qualcomm Inc (>> QUALCOMM, Inc.) to "outperform" from "neutral," based on share gains and expectation of better handset pricing. It named the cellphone chip supplier its new top pick among large-cap semiconductors.