Oscillation circuit and oscillator

An oscillation circuit comprising:

• a cross-coupled circuit having a first active element and a second active element that are differentially connected to each other,
• a capacitor connected between the drain terminal of the first active element and the drain terminal of the second active element,
• wherein the oscillation circuit oscillates in a resonance frequency of a resonator connected between the first active element and the second active element,
• a source terminal of the first active element is connected to GND through a first source load circuit,
• a source terminal of the second active element is connected to GND through a second source load circuit,
• a drain terminal of the first active element is connected to a voltage source through a first drain load circuit,
• a drain terminal of the second active element is connected to a voltage source through a second drain load circuit,
• a first source impedance includes an impedance of the first source load circuit and an impedance of the resonator,
• a first drain impedance includes an impedance of the first drain load circuit and an impedance of the capacitor,
• a second source impedance includes an impedance of the second source load circuit and the impedance of the resonator,
• a second drain impedance includes an impedance of the second drain load circuit and the impedance of the capacitor,
• the impedance of the capacitor is equal to a parallel capacitance of the resonator,
• the first source impedance is equal to or greater than the first drain impedance, and
• the second source impedance is equal to or greater than the second drain impedance.