Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 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 September 30,				Nine months ended September 30,
	Three months ended September 30,				Nine months ended September 30,
	2017		2016		2017		2016
Cost of sales	$	117	$	129	$	354	$	498
Research and development	396		365		1,212		1,006
Sales and marketing	434		376		1,341		645
General and administrative	932		864		3,031		3,671
Total stock-based compensation expense	$	1,879	$	1,734	$	5,938	$	5,820

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.



	Nine months ended September 30,
	Nine months ended September 30,
	2017		2016
Risk-free interest rate	2.31	%	1.47	%
Expected option life (in years)	6.63		6.59
Volatility rate	36	%	36	%
Dividend rate	—	%	—	%