This is a very simplified view of a high tech sector M&A Buy Side Process. Some of the timings can shift a little depending on the actual case. For example, the Letter of Intent will come before Due Diligence begins in earnest but the actual offer may come in the form of a range before due diligence begins or it may come afterwards.
It is not unusual for the whole process to last anywhere from 6 months to a year on average. However really rapid transactions have been known to occur within 3-4 months and really slow ones, in years!