Block from U+0250 to U+02AF. This block was introduced in Unicode version 1.1 (1993). It contains 96 codepoints.
The Wikipedia provides the following information on block IPA Extensions:
IPA Extensions is a block (0250–02AF) of the Unicode standard that contains full size letters used in the International Phonetic Alphabet (IPA). Both modern and historical characters are included, as well as former and proposed IPA signs and non-IPA phonetic letters. Additional characters employed for phonetics, like the palatalization sign, are encoded in the blocks Phonetic Extensions (1D00–1D7F) and Phonetic Extensions Supplement (1D80–1DBF). Diacritics are found in the Spacing Modifier Letters (02B0–02FF) and Combining Diacritical Marks (0300–036F) blocks.
With IPA's ability to use Unicode for the presentation of phonetic symbols, ASCII-based systems such as X-SAMPA or Kirshenbaum are being supplanted. Within the Unicode blocks there are also a few former IPA characters no longer in international use by linguists.
The IPA Extensions block has been present in Unicode since version 1.0, and was unchanged through the unification with ISO 10646. The block was filled out with extensions for representing disordered speech in version 3.0, and Sinology phonetic symbols in version 4.0.