Note 6 - Equity Incentive Plan (Tables)

3 Months Ended

Mar. 31, 2019

Notes Tables

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

	Three Months Ended March 31,
	2019			2018
Risk free interest rate	2.44%	-	2.54%	2.15%	-	2.37%
Expected volatility	44.34%	-	44.41%	38.74%	-	40.81%
Expected life (years)		3.5			4.5
Expected dividend yield		0.00%			0.00%

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

	Three Months Ended March 31,
	2019		2018
Cost of product revenue	$	92	$	(216	)
Research & development		177		210
Selling, general & administrative		1,117		7,571
Total stock-based compensation expense	$	1,386	$	7,565

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

	Three Months Ended March 31,
	2019		2018
Grants:
Stock Options		104,292		192,300
RSAs		–		64,578
RSUs		165,507		8,130
PSUs		114,500		–
Exercises:
Stock Options		500		11,425
SARs		–		–