Vco having a low sensitivity to noise on the power supply

Abstract

The present invention comprises a voltage controlled oscillator (VCO) circuit having high power supply noise rejection. The VCO circuit includes a VCO input for receiving a control voltage. A level shifter circuit is coupled to the VCO input. A first and second VCO cell are coupled to the level shifter circuit and are coupled to each other. The VCO circuit also includes a VCO output for transmitting a VCO output signal. A first source follower transistor is coupled to the first VCO cell to transmit a first voltage from the power supply to the first VCO cell. A second source follower transistor is coupled to the second VCO cell to transmit a second voltage from the power supply to the second VCO cell. A first and second load transistor are included in each VCO cell. They are directly coupled to receive the control voltage such that the VCO output signal is less sensitive to noise on the power supply and the VCO output signal remains stable. Additionally, the level shifter is coupled to control the first source follower transistor and the second source follower transistor such that the first voltage and the second voltage are insensitive to noise on the power supply.