Ring oscillator having a substantially sinusoidal signal

A ring oscillator comprising an odd number of inverters connected in a ring, and means for driving the ring oscillator so that it oscillates at a frequency sligthly less than its maximum oscillating frequency such that harmonics of said oscillating frequency are suppressed, said ring oscillator being formed entirely of CMOS elements, said ring being formed of more than two inverters connected in series, an output of the series of inverters being connected to an input of the series of inverters, each inverter being comprised of a PMOS field effect transistor having its source-drain circuit in series with an NMOS FET, means for connecting a source of each of the PMOS FETs to a voltage rail and the source of each of the NMOS FETs other than a first NMOS FET in the series of inverters to ground, the source of the first NMOS FET being connected via a source-drain circuit of a control NMOS FET to ground, and means for applying a control voltage to a gate of the control NMOS FET.

A ring oscillator comprising an odd number of inverters connected in a ring, and means for driving the ring oscillator so that it oscillates at a frequency slightly less than its maximum oscillating frequency such that harmonics of such oscillating frequency are suppressed, said ring oscillator being formed entirely of CMOS elements, comprising two rings of similar numbers of CMOS inverters, each ring having an odd number of CMOS inverters in excess of two, means connecting an output of each ring to an input of the same ring, means for cross-coupling the outputs of an even number of corresponding ones of the inverters of each ring via cross-coupling inverters, and means for controlling current flow via a control voltage in a last CMOS inverter of each ring feeding an output terminal.