Patent ID: 7733190

Claim:
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.