Patent ID: 8035453

Claim:
An oscillator circuit comprising: differential variable delay circuits coupled together to form a ring oscillator, wherein each of the differential variable delay circuits comprises first and second inputs and first, second, third, and fourth transistors, wherein a constant supply voltage is provided to sources of the first and the second transistors in each of the differential variable delay circuits, wherein a variable supply voltage is provided to sources of the third and the fourth transistors in each of the differential variable delay circuits, wherein gates of the first and the third transistors are coupled to the first input, wherein gates of the second and the fourth transistors are coupled to the second input, and wherein the oscillator circuit generates is operable to generate a periodic output signal having a frequency that varies based on changes in the variable supply voltage; and a fifth transistor operable to generate the constant supply voltage at a source of the fifth transistor based on a programmable input voltage.