Self-biased active VCO level shifter

A voltage-controlled oscillator (VCO) system, comprising:

• a VCO circuit that includes:
• first, second, third, and fourth transistors, each with a first terminal, a second terminal, and a control terminal,
• wherein said first terminal of said first transistor communicates with said first terminal of said second transistor, said control terminals of said third and fourth transistors communicate with said second terminals of said first and second transistors, respectively, and said control terminals of said second and first transistors are responsive to signals generated at said first terminals of said third and fourth transistors, respectively;
• and
• first and second capacitances, wherein first ends of said first and second capacitances communicate with said second terminals of said first and second transistors, respectively, and wherein second ends of said second and first capacitances communicate with said control terminals of said first and second transistors, respectively;
• a capacitance adjustment circuit that that communicates with said VCO circuit and that adjusts a net capacitance of said VCO circuit;
• and
• an output buffer that buffers an output signal of said VCO circuit and that adjusts an output impedance of said VCO system.