Patent ID: 6956442
Filing Date: 2005-10-18
Classification: H03K,H03L

Abstract:
1. A delay stage circuit of a ring oscillator for setting a delay value of the delay stage circuit and a corresponding frequency of operation of the ring oscillator, the delay stage circuit comprising: a differential transistor pair for receiving an input oscillation signal and for producing a corresponding output oscillation signal characterized by a delay, wherein the differential transistor pair is coupled to receive a bias signal set by an external bias circuit; an active load further comprising a pair of MOSFET devices, each having a drain coupled to a supply, a source coupled to a drain of one device of the differential transistor pair and a gate coupled to a selectable resistive load that is further coupled to the supply; and wherein the selectable resistive load comprises a plurality of resistive devices that, when coupled in series with a gate-to-source capacitance provided by the pair of MOSFET devices, generates a desired R-C time constant to define the delay of the differential transistor pair.