Doepfer

hi
i just bought a wasp filter module.  it sounds very cool.
i am curious if anyone could explain to the principle it operates 
upon?  i dont fully understand how electronics work.  i understand 
that op amps are basic circuits that are in many electronics.  i see 
a lot of op amp ICs when i go to a local store that sells electronic 
parts.

how does this circuit use "digital inverters" as analog op amps, and 
why won't it self oscillate?  the res all the way up does create a 
very grotesque and fantastic sound.  my understanding of filters is 
that the resonance is feeding the filter back into it self, thus 
oscillating at the tuned frequency (cutoff).

anyone who can answer in a simplified way, thanks.
---t