A fast CMOS voltage-controlled ring oscillator

A voltage-controlled ring oscillator based on variable capacitive loading is described. A prototype, fabricated in a 1.2 /spl mu/m CMOS-technology, has been tested. The results showed that it is capable to operate at a maximum frequency of 560 MHz. This design operates at 92% of the speed achievable by the same ring oscillator, but where the speed control circuits have been removed. An important feature of this oscillator is its tunability range, which goes from 277 to 560 MHz, or a factor of 2.0 between f/sub max/ and f/sub min/. This paper presents the simulations performed to optimize the performance of the circuit.<<ETX>>