Note 4 - Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2016

Notes Tables

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

	Three Months Ended June 30,				Six Months Ended June 30,
	2016		2015		2016		2015
Cost of design-to-silicon yield-solutions	$	956	$	914	$	2,041	$	1,801
Research and development		651		510		1,357		1,001
Selling, general and administrative		684		931		1,559		1,752
Stock-based compensation expense	$	2,291	$	2,355	$	4,957	$	4,554

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Three Months Ended June 30,						Six Months Ended June 30,
	2016			2015			2016			2015
Expected life (in years)		4.42			4.51			4.42			4.51
Volatility		43.58	%		46.8	%		44.26	%		46.7	%
Risk-free interest rate		1.30	%		1.41	%		1.25	%		1.34	%
Expected dividend		—			—			—			—
Weighted average fair value per share of options granted during the period	$	5.00		$	6.61		$	4.46		$	6.50

	Six months Ended June 30 ,
	2016			2015
Expected life (in years)		1.25			1.25
Volatility		44.15	%		54.21	%
Risk-free interest rate		0.50	%		0.26	%
Expected dividend		—			—
Weighted average fair value of purchase rights granted under the Purchase Plan	$	3.56		$	6.19

Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]

	Number of Options (in thousands)			Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Term (years)		Aggregate Intrinsic Value (in thousands)
Outstanding, January 1, 2016		1,764		$	7.88
Granted (weighted average fair value of $4.46 per share)		50		$	11.87
Exercised		(63	)	$	7.20
Canceled		(7	)	$	15.01
Expired		(75	)	$	13.79
Outstanding, June 30, 2016		1,669		$	7.73		4.87	$	10,719
Vested and expected to vest, June 30, 2016		1,660		$	7.70		4.84	$	10,704
Exercisable, June 30, 2016		1,523		$	7.17		4.49	$	10,539

Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]

	Shares (in thousands)			Weighted Average Grant Date Fair Value Per Share
Nonvested, January 1, 2016		1,166		$	17.03
Granted		50		$	11.87
Vested		(258	)	$	16.70
Forfeited		(42	)	$	17.27
Nonvested, June 30, 2016		916		$	16.83