Jim Parsons. Photo by Chris Pizzello/Invision/AP

American actor Jim Parsons' time on Broadway reportedly convinced him to quit 'The Big Bang Theory'.

The 45-year-old actor plays the part of Sheldon Cooper in the CBS sitcom - which is set to end at the conclusion of the upcoming series - and according to E! News, Jim decided the time had come to walk away from the show following his stint in the Ryan Murphy-produced 'The Boys in the Band'.

The actor had been considering the decision for a number of months, and he's pleased that the show is going out on a high, while it's still popular among long-time fans.

The decision to end the show was announced earlier this week, and Jim's co-star Kaley Cuoco admitted she was "drowning in tears" after the news was revealed.

The actress - who has played the role of Penny since the series began in 2007 - revealed she was devastated by the decision, but she also promised fans that the finale will be "the best season" ever.

Alongside a professional photo of herself with some of her cast mates, Kaley wrote on Instagram: "This ride has been a dream come true and as life changing as it gets. No matter when it was going to end , my heart would have always been broken in two. Drowning in tears, we promise to bring you the best season yet. To the fans, our crew, families, Chuck Lorre, Warner Brothers , CBS, and everyone who has supported us for so many years, thank you. We are goin out with a bang @bigbangtheory_cbs (sic)"

'The Big Bang Theory' is already the longest-running multi-camera series in TV history and its final season is set to begin in the US in September.