US 7,321,269 B2
High frequency ring oscillator with feed-forward paths
Alan J. Drake, Round Rock, Tex. (US); Fadi H. Gebara, Austin, Tex. (US); and Jeremy D. Schaub, Austin, Tex. (US)
Assigned to International Business Machines Corporation, Armonk, N.Y. (US)
Filed on Jul. 19, 2005, as Appl. No. 11/184,352.
Prior Publication US 2007/0018737 A1, Jan. 25, 2007
Int. Cl. H03K 3/03 (2006.01); H03B 27/00 (2006.01)
U.S. Cl. 331—57  [331/45; 331/183] 12 Claims
OG exemplary drawing
 
1. A voltage controlled ring oscillator comprising:
a number N primary inverting stages each having an input and an output, wherein the N primary inverting stages are coupled in series with the output of the Nth primary inverting stage coupled back to the input of the first primary inverting stage; and
N modulating inverting stages each having a first input, a second input and an output, wherein the first input of modulating inverting stage numbered M is coupled to an input of a primary inverting stage numbered M from the N primary inverting stages, the output of modulating inverting stage numbered M is coupled to an output of the primary inverting stage numbered M from the N primary inverting stages, the second input of modulating inverting stage numbered M is coupled to an output of a primary inverting stage numbered (M+2)(modulo N) from the N primary inverting stages, and a signal level on the output of each of the N modulating inverting stages is varied in response to a voltage level of a common control voltage and corresponding voltage levels on the first and second inputs of each of the N modulating inverting stages, and
wherein the modulating inverting stages each comprises:
a first inverter having an input coupled to the first input of the modulating inverting stage and an output;
a first pass gate having an input coupled to the output of the first inverter, a pass gate output coupled to the output of the modulating inverting stage, and a first control input coupled to the common control voltage;
a second inverter having an input coupled to the second input of the modulating inverting stage and an output;
a second pass gate having an input coupled to the output of the second inverter, a pass gate output coupled to the output of the modulating inverting stage, and a second control input coupled to the common control voltage; and
a third inverter having an input coupled to the second input of the modulating inverting stage and output coupled to the output of the second inverter.