The Wales star swapped Ospreys, where he started his career, for Saints in the summer of 2018 - and he hasn't looked back.
Biggar has been given a new lease of life by his move to England, flourishing under the tuition of the likes of Chris Boyd and Sam Vesty.
He played a key role last season, steering Saints to a top four finish in the Gallagher Premiership.
He helped Wales to reach the World Cup semi-finals in Japan and has since returned to his club, playing a starring role in wins against Lyon and Benetton.
And Biggar, who started in last Saturday's defeat to Leinster, said: "I find I'm learning things each day and becoming a better player each day.
"I genuinely think I've become a better player from being up here and being involved in the setup.
"It's down to the coaches but it's also down to the lads we've got here as well because they are just driving the standards and the enthusiasm.
"It's definitely the happiest I've ever been on a rugby field, which makes life a lot easier.
"We've had a really good start and I don't want us to get carried away and think we're the best team in the world because we're not, but if we can carry on doing what we've done in the past five or six weeks it gives us a real good chance to be in the mix come knockout time."
On the influence of Boyd and Vesty, Biggar said: "Chris (Boyd) gets all the plaudits and so he should because he's the best guy I've worked for and wanted to work for - and I've had a lot of good coaches over the years!
"I think all the guys feel the same because they don't want to let him down.
"Sam Vesty deserves huge amounts of credit also because he's ultra-positive and competitive.
"He wants us to be better and he wants us to come out with something at every training session and meeting.
"He wants us to have learned something and it's infectious when you're around guys like that and young guys who want to learn so much."