In the prior posting I showed a link that discusses a popular servo controller chip that was used for decades internally for many hobby servos: Technical Reference Info for Servos
While no longer being used, I'm sure most of the inexpensive servos are still using the same general design just with smaller chips.
In figure 1 of the embedded data shows the motor connection on the right hand side. It is being driven by a H-drive bridge. The artical discusses the operation of the servo controller in some detail.
Lefty