What is minimum GPA for getting PhD in Germany?
As flo said, it totally depends on the university.

In principle, you can become PhD student at any German university if you


Have someone eligible (normally a professor in the department) who declares that she/he will supervise you, and
You meet the requirements from the examination regulations for the PhD.


In the majority of cases, the examination regulations can be found on the web. Many departments do not list a formal "grade" requirements, but some do. Typically, the grades are only given in German style, so there is room for interpretation when translating foreign grades. GPAs are pretty much unknown in Germany. Admission officers will look at the grades (e.g., A-F, where F means fail) and if the institution where the grade has been awarded is "OK". Summary grades are expressed in the same system as the individual grades. To make this part of the answer complete, as you are probably aware, it is normally a requirement to have a Masters degree before you can start with a PhD.

Structured programs, such as graduate schools, typically have their own rules on top of these. Again, standard vary, and you should be able to find some information on the home page of the respective graduate school.