The Robins sold out their ticket allocation for Saturday's clash a fortnight ago and will be backed at St James's Park by 2,800 fans.
Johnson, who has promised not to sit back and defend, expects his players to make the near-600 mile trip to the north east a fruitful one.
He told the Bristol Evening Post: "We owe it to those 2,800 fans to give it a go. Our supporters spend a lot of money following the boys all over the country and they always give them fantastic backing away from home.
"Like us, they will have been looking forward to this game ever since the fixture list came out and many of them are staying over and making a weekend of it.
"They will be heavily outnumbered by nearly 40,000 Newcastle fans, but that won't stop them singing their hearts out and getting behind the team. The least we can do is ensure they get to watch a proper, competitive game."