Note 11 - Equity Incentive Plan (Tables)

9 Months Ended

Sep. 30, 2021

Notes Tables

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

	Three Months Ended September 30,				Nine Months Ended September 30,
	2021		2020		2021		2020
Cost of revenue	$	142	$	202	$	485	$	564
Research and development		360		206		1,003		558
Selling, general and administrative		2,361		1,512		6,431		2,832
Total stock-based compensation expense	$	2,863	$	1,920	$	7,919	$	3,954

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

	Number of Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2020		896,819		$	41.50
Granted		493,628		$	37.67
Exercised		(27,851	)	$	34.62			$	234
Forfeited and canceled		(177,604	)	$	44.32
Outstanding as of September 30, 2021		1,184,992		$	39.65		8.5	$	4,654
Vested, September 30, 2021		304,172		$	44.01		7.3	$	812
Vested and expected to vest, September 30, 2021		1,184,992		$	39.65		8.5	$	4,654

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

	Nine Months Ended September 30,
	2021		2020
Risk-free interest rate		0.30% – 0.68%		0.21% – 1.59%
Expected life of options (in years)		4.0 – 6.3		4.0 – 6.3
Dividend yield		-%		-%
Expected stock price volatility		54.80% –56.06%		46.48% –52.99%

Schedule of Nonvested Restricted Stock Units Activity [Table Text Block]

	Number of Shares			Weighted Average Fair Value
Outstanding as of December 31, 2020		233,239		$	37.50
Granted		308,243			35.42
Vested		(90,013	)		37.63
Forfeited and cancelled		(48,624	)		35.69
Outstanding as of September 30, 2021		402,845		$	36.10

Schedule of Nonvested Performance-based Units Activity [Table Text Block]

	Number of Shares			Weighted Average Fair Value
Outstanding as of December 31, 2020		178,297		$	35.93
Granted		-			-
Vested		-			-
Forfeited and cancelled		(18,500	)		37.02
Outstanding as of September 30, 2021		159,797		$	35.80