Of any kind... I think the uA741 is about as open as any IC design can possibly be at this point. Still available from many places. Here is one. http://www.

Of any kind... I think the uA741 is about as open as any IC design can possibly be at this point. Still available from many places. Here is one. http://www.ti.com/lit/ds/symlink/ua741.pdf http://www.ti.com/lit/ds/symlink/ua741.pdf