STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2015

Schedule of non-cash stock-based compensation expense by department


	December 31,
	2015		2014		2013
Cost of sales	$	876	$	279	$	—
Research and development		3,744		4,149		2,817
General and administrative		9,358		5,575		3,054
Sales and marketing		4,072		1,517		1,873
Total stock-based compensation	$	18,050	$	11,520	$	7,744

Schedule of valuation assumptions


	Year Ended
	December 31,
	2015	2014	2013
Option Plan Shares
Risk-free interest rates	1.5% - 1.92%	1.96% - 2.01%	0.94% - 1.73%
Expected term (in years)	6.25 - 6.6	6	6
Expected volatility	67.1% - 73.2%	77.6% - 80.8%	82.9% - 84%
Dividend yield	0%	0%	0 %
Weighted average fair value per share of options granted during the period	$15.81	$ 10.05	$ 8.12
ESPP Shares
Risk-free interest rates	0.25% - 0.75%	0.1% - 0.5%	0.1% - 0.33%
Expected term (in years)	0.5 - 2	0.5 - 2	0.5 - 2
Expected volatility	51.2% - 110%	42.5% - 62.7%	39.1% - 45.6%
Dividend yield	0%	0%	0 %
Weighted average fair value per share of stock purchase rights granted during the period	$ 4.67	$ 6.3	$ 3.13

Summary of stock option activity under the Stock Plans


				Weighted
		Weighted		Average
		Average		Remaining	Aggregate
		Exercise		Contractual	Intrinsic
Options	Shares	Price		Term (Years)	Value(1)
(Aggregate intrinsic value in thousands)
Outstanding, January 1, 2013	6,181,936	$	2.62
Granted	290,570		11.36
Exercised	(274,919)		5.17
Forfeited	(135,000)		10.08
Outstanding, December 31, 2013	6,062,587	$	2.78	6.6
Granted	266,477		14.28
Exercised	(1,378,372)		1.91
Forfeited	(16,375)		6.37
Outstanding, December 31, 2014	4,934,317	$	3.63	5.2
Granted	340,978		23.51
Exercised	(281,315)		4.44
Forfeited	(57,386)		16.99
Outstanding, December 31, 2015	4,936,594	$	4.80	4.5	$	28,126
Exercisable, December 31, 2015	4,219,865	$	2.69	3.9	$	27,585
Vested and expected to vest, December 31, 2015	4,900,829	$	4.71	5.2	$	27,601

(1)

The aggregate intrinsic value of options outstanding at December 31, 2015 is calculated as the difference between the exercise price of the underlying options and the market price of the Company’s common stock for the 4,936,594 options that had exercise prices that were lower than the $9.23 market price of our common stock at December 31, 2015. The aggregate intrinsic value of options exercisable at December 31, 2015 is calculated as the difference between the exercise price of the underlying options and the market price of the Company’s common stock for the 4,219,865 options that had exercise prices that were lower than the $9.23 market price of our common stock at December 31, 2015. The total intrinsic value of options exercised during the years ended December 31, 2015, 2014 and 2013 was $3.6 million, $29.2 million, $1.9 million, respectively, determined as of the date of exercise.

Summary of restricted stock and restricted stock unit activity under the Stock Plans


		Weighted
	Restricted	Average Grant
	Shares	Date Fair Value
Outstanding, January 1, 2013	813,955	$	8.51
Granted	1,147,553		11.76
Released	(344,611)		8.56
Forfeited	(466,203)		9.73
Outstanding, December 31, 2013	1,150,694	$	11.23
Granted	926,171		15.61
Released	(491,370)		11.17
Forfeited	(44,381)		12.44
Outstanding, December 31, 2014	1,541,114	$	13.86
Granted	2,895,818		15.23
Released	(578,033)		13.77
Forfeited	(414,205)		20.84
Outstanding, December 31, 2015	3,444,694	$	14.19

Summary of information relating to outstanding and exercisable stock options

The following table summarizes information relating to currently outstanding and exercisable stock options as of December 31, 2015:


	Outstanding				Exercisable
		Weighted
		Average	Weighted			Weighted
		Remaining	Average			Average
	Number of	Contractual	Exercise		Number of	Exercise
Exercise Price	Options	Life (Years)	Price		Options	Price
$0.00 - $3.00	3,186,500	3.3	$	1.10	3,186,500	$	1.10
$3.01 - $6.00	402,822	4.7		4.40	402,822		4.40
$6.01 - $9.00	146,991	5.5		7.89	146,991		7.89
$9.01 - $12.00	619,087	6.5		9.66	415,393		9.55
$12.01 - $15.00	233,000	8.2		13.96	58,250		13.96
$15.01 - $18.00	22,227	8.6		16.52	9,909		16.52
$18.01 - $24.00	313,359	9.2		23.38	—		—
$24.01- $26.98	12,608	9.1		26.98	—		—
	4,936,594	4.5	$	4.80	4,219,865	$	2.69

Summary of shares of authorized common stock reserved for issuance


Shares reserved for issuance
2010 Option Plan		6,159,082
2010 Purchase Plan		363,392
		6,522,474

2010 Employee Stock Purchase Plan

Stock-based compensation

Schedule of shares of common stock issued


		Weighted Average
Offering period ended	Number of Shares	price per Share
April 30, 2015	56,635	$	13.02
October 31, 2015	120,150	$	7.72