George Soros, the billionaire investor who said in July he was converting his New York-based firm to a family office, added shares of Amazon.com Inc. and Motorola Solutions Inc. in the third quarter, and sold most of his stake in Ralph Lauren Corp., according to a regulatory filing.

Soros Fund Management LLC bought 193,271 shares of Seattle- based Amazon, bringing its position to 206,016 shares, valued at $44.6 million at the end of September.

Soros added 934,200 shares of Motorola Solutions, bringing his stake to 6.6 million shares, valued at $276.4 million at the end of the quarter.

The firm, which is based in New York and oversees about $25 billion in assets, held about $4.9 billion in stocks at the end of the quarter, according to the filing with the U.S. Securities and Exchange Commission.

Motorola Solutions, the maker of bar-code scanners and walkie-talkies, split in January from Motorola Mobility Holdings Inc. The Schaumburg, Illinois-based company is Soros’s biggest holding.

Soros sold 820,000 shares of Ralph Lauren. He still owns 174,611 shares valued at $22.7 million of the New York-based clothing company.

Michael Vachon, a spokesman for Soros, declined to comment on the filing.