Patent ID: 8564378
Filing Date: 2013-10-22
Classification: H03B

Abstract:
1. A voltage-controlled oscillating circuit for being connected to a resonant element, comprising: a first node and a second node for being connected respectively to opposite ends of said resonant element; a differential amplifying circuit including first and second input terminals, which constitute a pair of differential input terminals, and first and second output terminals, which constitute a pair of differential output terminals; first and second voltage-controlled variable capacitors connected respectively to said first node and said second node; first and second load capacitors connected respectively to said first and second output terminals; first and second follower circuits, such as emitter follower circuits, connected respectively to said first and second output terminals; a first feedback capacitor and a third voltage-controlled variable capacitor which are connected in series to an output terminal of the first follower circuit; and a second feedback capacitor and a fourth voltage-controlled variable capacitor which are connected in series to an output terminal of the second follower circuit; wherein said first and second nodes are connected respectively to said first and second input terminals, an output signal of the first follower circuit is fed back to said second node through said first feedback capacitor and said third voltage-controlled variable capacitor, an output signal of the second follower circuit is fed back to said first node through said second feedback capacitor and said fourth voltage-controlled variable capacitor, and a control voltage is applied to the first to fourth voltage-controlled variable capacitors.