Striker Connell arrives on a short-term deal until the end of the season while Ravenhill has penned an 18-month contract, with the duo having their Bantams contracts cancelled by mutual consent.
They could now both be involved in what is new Cobblers boss Chris Wilder's first game in charge at Cheltenham on Saturday.
Connell, 30, has scored 95 times in 391 career appearances taking in the likes of Bournemouth, Torquay, Hereford, Brentford, Grimsby, Swindon and Bradford.
Meanwhile, Ravenhill, 33, is no stranger to Cobblers fans having enjoyed an eight-match loan spell at Sixfields which came to an end just before Christmas.
Bradford boss Phil Parkinson told the club's official website: "Alan hasn't featured for the club for a bit now and he was always going to move on in this window. He is a player who needs games and we hope he will get them at Northampton.
"Ricky's situation is slightly different because he has been starting some games recently because of Doyley's (Nathan Doyle) injury. We had an agreement with Ricky, however, that if he got offered a longer contract somewhere else then we'd look at letting him go.
"He had an opportunity to get a longer deal at Northampton and he wanted to take it.
"Ricky's departure now gives us the opportunity to maybe bring in another midfielder to see us over between now and the end of the season."