Note 15 - Segment and Geographic Information (Tables)

12 Months Ended

Mar. 31, 2017

Notes Tables

Revenue from External Customers by Geographic Areas [Table Text Block]

	Year Ended March 31,
	2017		2016		2015
United States	$	81,499	$	75,994	$	85,314
Europe and the Middle East:
Austria		2,313		1,836		2,290
Finland		2,178		1,899		1,669
France		9,553		9,076		7,917
Germany		37,919		33,215		32,866
Hungary		1,942		2,082		2,571
Italy		4,091		4,328		4,645
Netherlands		4,488		3,608		2,315
Russia		1,263		4,773		5,051
Sweden		1,694		2,155		4,460
Switzerland		2,311		2,789		2,569
Turkey		1,929		2,376		2,658
United Kingdom		14,042		13,502		19,832
Other		10,097		10,700		11,259
Asia Pacific:
China		84,447		79,575		83,597
Indonesia		2,160		2,128		3,224
Japan		6,995		9,271		8,469
Malaysia		4,692		4,662		5,580
Singapore		13,509		12,353		11,694
South Korea		19,282		23,215		22,371
Taiwan		2,051		3,151		2,688
Thailand		3,547		3,904		4,300
Other		1,557		1,929		1,148
Rest of the World:
India		4,315		4,293		5,163
Other		4,249		4,395		5,117
Total	$	322,123	$	317,209	$	338,767

Revenue from External Customers by Products and Services [Table Text Block]

	Year Ended March 31,
	2017		2016		2015
Power semiconductors	$	221,312	$	213,347	$	219,445
Integrated circuits		82,067		84,078		95,547
Systems and RF power semiconductors		18,744		19,784		23,775
Total	$	322,123	$	317,209	$	338,767

Schedules of Concentration of Risk, by Risk Factor [Table Text Block]

	Year Ended March 31,
	2017			2016			2015
Revenues:
Distributor A		12.3	%		12.2	%		10.2	%
Distributor B		10.8	%		less than 10	%		10.5	%

	March 31,
	2017			2016
Accounts Receivable:
Distributor A		15.2	%		18.2	%
Distributor C		10.5	%		less than 10	%

Summary of Net Revenues, Net Income of Domestic and Foreign Operations [Table Text Block]

	Year Ended March 31,
	2017		2016		2015
Net revenues:
Foreign	$	148,159	$	159,984	$	188,964
Domestic		173,964		157,225		149,803
Total	$	322,123	$	317,209	$	338,767
Net income:
Foreign	$	17,172	$	11,039	$	21,379
Domestic		4,176		3,702		2,361
Total	$	21,348	$	14,741	$	23,740

Long-lived Assets by Geographic Areas [Table Text Block]

	March 31,
	2017		2016		2015
Property, plant and equipment, net:
United States	$	25,284	$	26,792	$	27,740
Germany		15,594		14,506		13,228
Other countries		1,362		1,325		1,577
Total property, plant and equipment, net	$	42,240	$	42,623	$	42,545