Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 27, 2014	Sep. 28, 2013	Sep. 27, 2014	Sep. 28, 2013
Income Statement [Abstract]
Revenue	$ 86,570	$ 87,154	$ 282,527	$ 243,006
Costs and expenses:
Cost of products sold	35,759	40,778	122,603	113,365
Research and development	22,053	20,254	65,594	58,635
Selling, general and administrative	17,645	16,385	55,226	49,955
Amortization of intangible assets	737	737	2,211	2,223
Restructuring charges	2	85	16	257
Costs and expenses	76,196	78,239	245,650	224,435
Income from operations	10,374	8,915	36,877	18,571
Other income, net	53	346	1,268	240
Income before income taxes	10,427	9,261	38,145	18,811
Provision for income taxes	1,021	417	4,984	3,037
Net income	$ 9,406	$ 8,844	$ 33,161	$ 15,774
Net income per share:
Basic (in dollars per share)	$ 0.08	$ 0.08	$ 0.28	$ 0.14
Diluted (in dollars per share)	$ 0.08	$ 0.08	$ 0.28	$ 0.13
Shares used in per share calculations:
Basic (in shares)	118,643	116,055	117,661	115,730
Diluted (in shares)	120,970	117,349	120,449	117,093