Bull told the paper, “My knee had been troubling me since Christmas so I had a scan which revealed a small tear in the cartilage and we decided that whilst it's the close season it would be a good time to have the operation.
“It all went very well, the recovery time is quite quick, about four to six weeks, I had a similar operation before and recovered quickly from that so I'm hoping this will be the same,” said Bull.
The England National Game XI keeper has also started physiotherapy this week with Sue Bowen, in his bid to reach fitness as soon as possible.
“We've pencilled in a return for about the middle of July, I might have to miss out on one or two friendlies but I'll be back for the start of the season,” said Bull.
The shot-stopper had been attracting interest from league clubs but is happy to be staying on with the Shots, and going for promotion this season.
“This year we have got to build on the past two seasons which means automatic promotion. We've been in the Play-Offs for two years running now so we have to go one better and get back into the League.
“The Play-Offs will always be a safety net but really we'll be gunning for automatic promotion, it's what we all want. Having said that we've got to get the side together first as we haven't got a full squad yet,” added Bull.
However, the former QPR keeper isn't concerned that boss Terry Brown is taking his time to build a side.
Bull added: “If it was any other club I probably would be worried, but Terry's record in signings during the close season has always been second to none. I have faith that as long as he has the backing of the board, Terry will be able to bring in quality players who will help us achieve our goal.”