Note 7 - EMPLOYEE BENEFIT PLANS (Tables)

3 Months Ended

Mar. 31, 2022

Notes Tables

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

	2021 Purchase Plan			2010 Purchase Plan
	Three Months Ended March 31,			Three Months Ended March 31,
	2022			2021
Expected life (in years)		1.25			1.25
Volatility		48.90	%		34.25	%
Risk-free interest rate		0.86	%		1.43	%
Expected dividend		—			—
Weighted average fair value of purchase rights granted during the period	$	10.76		$	4.83

Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]

Stock-based compensation is estimated at the grant date based on the award’s fair value and is recognized on a straight-line basis over the vesting periods, generally four years. Stock-based compensation expense before taxes related to the Company’s stock plans and employee stock purchase plan was allocated as follows (in thousands):

	Three Months Ended March 31,
	2022		2021
Costs of revenues	$	728	$	652
Research and development		3,168		1,588
Selling, general and administrative		1,657		1,129
Stock-based compensation expenses	$	5,553	$	3,369

Share-based Payment Arrangement, Option, Activity [Table Text Block]

	Outstanding Options
				Weighted
		Weighted		Average
		Average		Remaining	Aggregate
	Number of	Exercise		Contractual	Intrinsic
	Options	Price		Term	Value
	(in thousands)	per Share		(Years)	(in thousands)
Outstanding, January 1, 2022	226	$	12.78
Granted	—		—
Exercised	(75)		9.06
Canceled	(3)		13.57
Expired	—		—
Outstanding, March 31, 2022	148	$	14.64	4.19	$	1,954
Vested and expected to vest, March 31, 2022	146	$	14.63	4.15	$	1,936
Exercisable, March 31, 2022	121	$	14.54	3.45	$	1,612

Share-based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block]

		Weighted
		Average Grant
	Shares	Date Fair Value
	(in thousands)	Per Share
Nonvested, January 1, 2022	1,872	$	18.24
Granted	275	$	27.90
Vested	(344)	$	19.73
Forfeited	(30)	$	18.43
Nonvested, March 31, 2022	1,773	$	19.45