Note 12 - Equity Incentive Plan (Tables)

6 Months Ended

Jun. 30, 2020

Notes Tables

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

	Six months ended June 30,
	2020				2019
Risk free interest rate		0.31%	-	1.59%		2.18%	-	2.54%
Expected volatility		46.48%	-	51.87%		44.05%	-	44.72%
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 June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Cost of product revenue	$	216	$	82	$	362	$	174
Research & development		156		91		352		268
Selling, general & administrative		1,868		1,270		1,319		2,387
Total stock-based compensation expense	$	2,240	$	1,443	$	2,033	$	2,829

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Grants:
Stock options		106,438		27,325		317,213		131,617
RSUs		83,476		8,000		184,107		173,507
PSUs		88,820		-		146,220		114,500
TSRs		104,638		-		104,638		-
Exercises:
Stock options		2,146		22,400		2,146		22,900
Forfeitures:
Stock options		20,625		38,163		54,103		39,072
RSAs		-		14,450		8,574		21,116
RSUs		8,483		22,000		72,166		22,500
PSUs		8,000		-		71,000		18,000
Expirations:
Stock options		200		2,855		563		18,862