Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2017

Compensation Expense Related to Stock-Based Compensation Plans

The compensation expense related to the Company’s stock-based compensation plans included in the accompanying Consolidated Statements of Operations was as follows (in thousands):



	Three months ended March 31,
	Three months ended March 31,
	2017		2016
Cost of sales	$	130	$	235
Research and development	412		297
Sales and marketing	470		(63		)
General and administrative	909		1,511
Total stock-based compensation expense	$	1,921	$	1,980

Estimated Fair Value of Each Stock Option Award

The estimated fair value of each stock option was determined on the date of grant using the Black-Scholes option valuation model with the following weighted-average assumptions for the option grants.



	Three months ended March 31,
	Three months ended March 31,
	2017		2016
Risk-free interest rate	2.33	%	1.46	%
Expected option life (in years)	6.63		6.46
Volatility rate	36	%	36	%
Dividend rate	—	%	—	%