The below tables represent the key components of Teradyne’s convertible senior notes:


	July 1, 2018		December 31, 2017
	(in thousands)
Debt principal	$	460,000	$	460,000
Unamortized discount		87,103		94,013

Net carrying amount of convertible debt	$	372,897	$	365,987


	For the Three Months Ended				For the Six Months Ended
	July 1, 2018		July 2, 2017		July 1, 2018		July 2, 2017
	(in thousands)
Contractual interest expense on the coupon	$	1,438	$	1,438	$	2,875	$	2,875
Amortization of the discount component and debt issue fees recognized as interest expense		3,477		3,308		6,911		6,576

Total interest expense on the convertible debt	$	4,915	$	4,746	$	9,786	$	9,451