Patent ID: 8810323
Filing Date: 2014-08-19
Classification: H03K,H03L

Abstract:
1. A ring oscillator, comprising: a plurality of differential inverters coupled to form a loop, each differential inverter having a differential pair of transistors configured to steer a tail current from a current source, the current source sourcing the tail current responsive to a bias voltage; and a bias circuit configured to generate the bias voltage such that a transconductance for each transistor in the differential pairs is proportional to a factor that is a function of a ratio of transistor widths within the bias circuit; wherein the bias circuit includes a PMOS current mirror mirroring current into a first NMOS transistor and a second NMOS transistor; wherein the PMOS current mirror comprises a first PMOS transistor and a second PMOS transistor; wherein a length L for each of the first and second PMOS transistors and for each of the first and second NMOS transistors is the same; and wherein a width W for each of the first and second PMOS transistors and for the first NMOS transistor is the same, and wherein a width for the second NMOS transistor has a width of X multiplied by W, where X is a proportionality factor greater than 1.