Stock-Based Compensation

6 Months Ended

Jun. 30, 2021

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

6.	Stock-Based Compensation

The Company uses the Black-Scholes option pricing model to calculate the fair value of stock option awards, whether they possess time-based vesting provisions or performance-based vesting provisions, and awards granted under the Vicor Corporation 2017 Employee Stock Purchase Plan (“ESPP”), as of

heir

grant date.

Stock-based compensation expense was as follows (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020

Cost of revenues	$	252	$	277	$	480	$	396
Selling, general and administrative		779		1,030		1,632		1,467
Research and development		536		629		1,026		783

Total stock-based compensation	$	1,567	$	1,936	$	3,138	$	2,646

Compensation expense by type of award was as follows (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020

Stock options	$	1,336	$	1,737	$	2,667	$	2,243
ESPP		231		199		471		403

Total stock-based compensation	$	1,567	$	1,936	$	3,138	$	2,646

The increase in stock option compensation expense for the six months ended June 30, 2021 compared to the six months ended June 30, 2020, was primarily due to an increase in the number of stock options granted and higher stock-based compensation expense associated with June 2020 stock option awards.