The Saints made it five wins on the bounce with a tight 22 v 15 victory over Newcastle at Kingston Park at the weekend.
A late try from Chris Ashton clinched the victory after the hosts had fought back after a Ben Foden try and a Stephen Myler penalty had put Northampton into a half-time lead.
The Heineken Cup semi-finalists have a busy period before of their last four tie with Perpignan with Premiership games away to Gloucester and London Irish ahead of them this week.
Perpignan's preparations continued with an impressive 23 v 16 victory over second-place Racing Metro.
Nicolas Laharrague and Jonathan Wisniewsk exchanged early penalties before Joffrey Michael scored the games opening try on 53 minutes. Lagarrague converted and then added the extras to Rudolf Coetzee's try a few minutes later.
Sebastien Chabel scored a late consolation try for the visitors but Perpignan were too far ahead and deserved their victory at the Stade Aime Giral.
Heineken Cup semi-final: Leinster v Toulouse (Saturday April 30)
Leinster proved to strong for Ulster winning 34 v 26 as second hosted third in the Magners League.
The hosts had secured the try bonus point before the break after tries from Richardt Strauss, Luke Fitzgerald, Shane Horgan and Heinke van der Merwe. Hogan added another in the second period before Ulster fought back but Leinster were far too strong and clinical.
The visitors to the Aviva Stadium for the Heineken Cup semi-final Toulouse didn't have such good fortunes in their match on the weekend as Guy Noves men lost 22 v 9 away to Toulon.
The reigning European Champions still have a comfortable lead at the helm of the Top 14 but will be looking for an improvement when they host Bourgoin this weekend.
Amlin Challenge Cup semi-final: Stade Francais v Clermont (Friday April 29)
Clermont Auvergne received a huge confidence boost ahead of their Amlin Challenge Cup semi-final against Stade Francais by beating their opponents 20 v 12 in Paris in the Top 14.
The result lifts the visitors up to fourth in the table while Stade remain in tenth in the race for the end of season play-offs.
Clermont held a 10 v 0 lead at the break after a Kini Murimurival try and five points from the boot of Morgan Para.
Julien Dupuy reduced the deficit with an early second half penalty before Julien malzieu clinched the victory with a 53rd minute try. Parra converted and James Brock added a late penalty for the visitors.
Lionel Beauxis kicked nine further points for Stade but it wasn't enough to prevent their 13th defeat of the season.
Amlin Challenge Cup semi-final: Munster v Harlequins (Saturday April 30)
Munster secured themselves a home semi-final in the Magners League play-off's with two games to spare as they continued their run on fine form at the Parc y Scarlets, beating Welsh side the Scarlets 13 v 6.
The former European Champions made 11 changes to their side for the domestic clash but a try from Simon Zebo and eight points from the boot of Paul Warwick saw them home as they increased their lead at the top of the table to 14 points.
It wasn't such good news for their Amlin Challenge Cup semi-final opponents Harlequins who lost 19 v 15 to Bath at the Rec.
All of the visitor's points came from the boot of inspirational fly-half Nick Evans but Conor O'Shea's side will be looking for more next weekend when they travel to bottom-placed side Leeds Carnegie.