In a Colpitt's oscillator where two capacitors and one inductor determine the frequency of oscillation. Since Colpitt’s oscillator is a high frequency oscillator, its inductor value will be in µH and capacitor in pF. The circuit oscillates when the components are suitably selected to satisfy the Barkhausen criteria (βA=+1(feedback factor must be unity)) "A" is the gain of the amplifying element and "β" is the transfer function of the feedback path, so βA is loop gain around the feedback loop of the circuit. Also there must be a positive feedback. i.e., the phase shift around the loop is zero or an integer multiple of 2π.