Expected behavior the button to link to a url

Actual behavior not happening

I am trying to link from a button. Could you provide a working demo please? My code does not seem to work when I enter a url into it. Original code here:

 <a class="btn btn-outline-white btn-sm">
                          <i class="fas fa-volume-up left"></i> Play Audio</a>

Resources (screenshots, code snippets etc.) My code:

<a target="_blank" href"" class="btn btn-outline-white btn-sm">
                          <i class="fas fa-volume-up left"></i> Play Audio</a>