US Patent 9252753 Quadrature output ring oscillator and method thereof

Various circuits are described, which sustain an oscillation using a combination of four primary inverters, four feedforward inverters, and four coupling resistors for outputting a quadrature output signal while avoiding contention between a primary inverter and a feedforward inverter. In one configuration, a circuit includes four primary inverters configured in a ring topology, four coupling resistors uniformly interposed in the ring among the four primary inverters, and four feedforward inverters forming four sub-feedback loops, respectively, each sub-feedback loop comprising two primary inverters, one coupling resistor, and one feedforward inverter. In a further embodiment, the circuit further comprises a voltage-to-current converter is for receiving a control voltage and outputting a supply current to the four primary inverters and the four feedforward inverters. A corresponding method is also provided.