Note 6 - Equity Incentive Plan (Tables)

3 Months Ended

Mar. 31, 2017

Notes Tables

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

	Three Months Ended March 31,
	2017			2016
Risk free interest rate	1.70%	-	1.78%	1.16%	-	1.40%
Expected volatility	43.47%	-	44.30%	50.84%	-	51.61%
Expected life (years)		4.0			4.5
Expected dividend yield		0.00%			0.00%

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

	Three Months Ended March 31,
	2017		2016
Cost of product revenue	$	97	$	13
Research & development		10		102
Selling, general & administrative		1,075		702
Total share-based compensation expense	$	1,182	$	817