Note 6 - Equity Incentive Plan (Tables)

9 Months Ended

Sep. 30, 2019

Notes Tables

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

	Nine Months Ended September 30,
	2019			2018
Risk free interest rate	1.41%	-	2.54%	2.15%	-	2.82%
Expected volatility	44.27%	-	46.21%	37.12%	-	45.61%
Expected life (years)		3.5		4.0	-	4.5
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,
	2019		2018		2019		2018
Cost of product revenue	$	114	$	39	$	288	$	(205	)
Research & development		50		239		318		690
Selling, general & administrative		1,147		899		3,534		9,579
Total stock-based compensation expense	$	1,311	$	1,177	$	4,140	$	10,064

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

	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Grants:
Stock Options		87,250		18,500		218,867		228,300
RSAs		-		-		-		64,578
RSUs		9,000		3,624		185,507		11,754
PSUs		9,000		-		123,500		-
Exercises:
Stock Options		488,586		-		511,486		284,548
SARs		-		-		-		-