Note 12 - Equity Incentive Plan (Tables)

9 Months Ended

Sep. 30, 2020

Notes Tables

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

	Nine months ended September 30,
	2020			2019
Risk free interest rate	0.21%	-	1.59%	1.41%	-	2.54%
Expected volatility	46.48%	-	52.99%	44.27%	-	46.21%
Expected life (years)	4.0	-	6.3		3.5
Expected dividend yield		0.00%			0.00%

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

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Cost of product revenue	$	202	$	114	$	564	$	288
Research & development		206		50		558		318
Selling, general & administrative		1,512		1,147		2,832		3,534
Total stock-based compensation expense	$	1,920	$	1,311	$	3,954	$	4,140

Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Grants:
Stock options		85,345		87,250		402,558		218,867
RSUs		34,697		9,000		218,804		185,507
PSUs		16,077		9,000		162,297		123,500
TSRs		-		-		104,638		-
Exercises:
Stock options		-		488,586		2,146		511,486
Forfeitures:
Stock options		32,629		42,566		86,732		81,638
RSAs		-		1,975		8,574		12,533
RSUs		17,937		7,500		90,103		19,100
PSUs		19,000		4,500		90,000		13,500
Expirations:
Stock options		3,083		25,697		3,646		44,829