The Company is organized and operates as one reportable segment, the design, development, manufacture and marketing of integrated circuits and related components for use primarily in the high-voltage power-conversion market. The Company’s chief operating decision maker, the Chief Executive Officer, reviews financial information presented on a consolidated basis for purposes of making operating decisions and assessing financial performance.

The Company’s top ten customers accounted for approximately 79% of net revenues for the three months ended March 31, 2021, and approximately 55% in the corresponding period of 2020. A significant portion of these revenues are attributable to sales of the Company’s products to distributors of electronic components. These distributors sell the Company’s products to a broad, diverse range of end users, including original equipment manufacturers, or OEMs, and merchant power supply manufacturers. Sales to distributors were $134.2 million in the three months ended March 31, 2021, and $83.5 million for the corresponding period of 2020. Direct sales to OEMs and power-supply manufacturers accounted for the remainder.

The following customers represented 10% or more of the Company’s net revenues for the respective periods:

*	Total customer revenue was less than 10% of net revenues.

No other customers accounted for 10% or more of the Company’s net revenues in the periods presented.

Concentration of Credit Risk

Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash investments and trade receivables. The Company does not have any off-balance-sheet credit exposure related to its customers. As of March 31, 2021, and December 31, 2020, 86% and 90%, respectively, of accounts receivable were concentrated with the Company’s top ten customers.

The following customers represented 10% or more of accounts receivable:


	March 31,		December 31,
Customer	2021		2020
Avnet	58	%	50	%
Powertech Distribution Ltd.	*		10	%

* Total customer accounts receivable was less than 10% of accounts receivable.

No other customers accounted for 10% or more of the Company’s accounts receivable in the periods presented.

Geographic Net Revenues

The Company markets its products globally through its sales personnel and a worldwide network of independent sales representatives and distributors. Geographic net revenues, based on “bill to” customer locations, for the three months ended March 31, 2021, and March 31, 2020, were as follows:


	Three Months Ended
	March 31,
(In thousands)	2021		2020
United States of America	$	4,100	$	2,713
Hong Kong/China		118,730		60,413
Taiwan		6,442		6,479
Korea		12,489		10,357
Western Europe (excluding Germany)		7,130		10,035
Japan		4,647		3,905
Germany		7,006		5,567
Other		13,193		10,195
Total net revenues	$	173,737	$	109,664