Patent ID: 6954110

Claim:
A ring oscillator comprising: a plurality of delay cells coupled in series as a ring; and a replica cell coupled to the delay cells to provide at least one bias signal to the delay cells, the replica cell including a differential transistor pair formed of a first transistor and a second transistor, the first transistor having a first terminal and a second terminal coupled to the first terminal, the second transistor having a first terminal and a second terminal coupled to the first terminal of the second transistor, the first transistor also having a third terminal and the second transistor also having a third terminal coupled to the third terminal of the first transistor; wherein the replica cell further includes: a first active resistor connected between a power supply and the drain terminal of the first transistor; and a second active resistor connected between the power supply and the drain terminal of the second transistor; wherein: the first active resistor includes a third transistor coupled in parallel with a fourth transistor that is diode-connected; and the second active resistor includes a fifth transistor coupled in parallel with a sixth transistor that is diode-connected.