Note 6 - Equity Incentive Plan (Tables)

6 Months Ended

Jun. 30, 2019

Notes Tables

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

	Six Months Ended June 30,
	2019			2018
Risk free interest rate	2.18%	-	2.54%	2.15%	-	2.75%
Expected volatility	44.05%	-	44.72%	37.12%	-	40.81%
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 June 30,					Six Months Ended June 30,
	2019		2018			2019		2018
Cost of product revenue	$	82	$	(28	)	$	174	$	(244	)
Research & development		91		241			268		451
Selling, general & administrative		1,270		1,109			2,387		8,680
Total stock-based compensation expense	$	1,443	$	1,322		$	2,829	$	8,887

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Grants:
Stock Options		27,325		17,500		131,617		209,800
RSAs		-		-		-		64,578
RSUs		8,000		-		173,507		8,130
PSUs		-		-		114,500		-
Exercises:
Stock Options		22,400		273,123		22,900		284,548
SARs		-		-		-		-