This is MOSFET Clapp oscillator example circuit. Clapp oscillator is a type of Colpitts Oscillator. Above circuit designed with 2n7000 Small signal N-Channel MOSFET. Oscillation frequency depends on tank circuit resonant frequency. Tank circuit consist on L1,C1,C2 and C3. Resonant frequency formula is given under. In practical oscillation frequency may vary due to MOSFET biasing and transient response.

f_0 = \frac{1 }{2\pi} \sqrt{\frac{1}{L1 } (\frac{1}{C1} +\frac{1}{ C2}+\frac{1}{C3})}