Can I downgrade my Nexus One from Android 2.3.6 (Gingerbread) to Android 2.2 (Froyo)?

So I was wondering whether it's possible to downgrade my old Nexus One which is currently on gingerbread back to Froyo. If so, how do I go about this? I don't know much about downgrading on Android, but I think I have to root the device first and then flash a stock ROM. If that's the case, where could I find Android 2.2 ROM for my Nexus One? Any help is appreciated.