NEW YORK -- Multi-billionaire George Soros has purchased more than 76 million convertible notes of Mentor Graphics during the last quarter, making him the second high-profile investor to take an interest in the EDA company.

Soros this week disclosed the purchase of the notes, valued at $79.5 million. A convertible note is a type of secured debt that contains an option where the note will be converted into a predefined amount of the issuer's (Mentor's) shares.

This year, Carl Icahn, known for buying up large stakes in companies and breaking them up, has directly or indirectly accumulated more than 16.1 million shares of Mentor, or about 14% of the firm. Icahn Capital LP, Icahn's hedge fund, also owns 2.86 million shares of Cadence stock, or about 1% of the company.