Patent ID: 7289002

Claim:
A voltage controlled oscillator, comprising: an inductance-capacitance (LC) tank which is supplied with a power supply voltage and oscillates at a frequency, the LC tank comprising a first node to which an end of a first inductor and an anode of a first variable capacitor are coupled, and a second node to which an end of a second inductor and an anode of a second variable capacitor coupled; a negative resistor which comprises first and second N-channel metal oxide semiconductor field effect transistors, the negative resistor having a negative resistance to sustain the oscillation of the LC tank; a direct current block which comprises a first capacitor through which the second node is coupled to a gate of the first N-channel metal oxide semiconductor field effect transistor, and a second capacitor through which the first node is coupled to a gate of the second N-channel metal oxide semiconductor field effect transistor, and removing a direct current component from the power supply voltage; an alternating current block which comprises a first resistor through which gates of the first and a third N-channel metal oxide semiconductor field effect transistors are coupled, and a second resistor through which gates of the second and a fourth N-channel metal oxide semiconductor field effect transistors are coupled, the alternating current block applying an alternating current voltage having passed through the direct current block to the gates of the first and second N-channel metal oxide semiconductor field effect transistors; a first current mirror which comprises the third and fourth N-channel metal oxide semiconductor field effect transistors, and allows a current to symmetrically flow in the complementary metal oxide semiconductor voltage controlled oscillator, a gate of the third N-channel metal oxide semiconductor field effect transistor being coupled to the first resistor, a gate of the fourth N-channel metal oxide semiconductor field effect transistor being coupled to the second resistor, and a drain and the gate of the third N-channel metal oxide semiconductor field effect transistor being coupled to a reference voltage supply; and the reference voltage supply which applies a direct current voltage to the drain and gate of the third N-channel metal oxide semiconductor field effect transistor to supply a voltage to the first current mirror.