This is a Colpitts oscillator in a common-emitter configuration:
For oscillation to occur, there must be a positive feedback. But I'm confused how can this oscillator provide a 360° degree turn for the input signal.
At time t=0, DC current passes through RF choke and goes to C1 branch and L-C2 branch which both goes straight to ground. I added the polarity for C1, C2, and L above. From what I can see, the polarity for C2 forward biases more the base-emitter diode thus the collector current sinks and collector voltage decreases. This seems to contradict the preceded polarity (which is positive). With this, I think voltage will not build-up and oscillate.
What am I missing?