Clock generation circuit with fast-startup standby mode

A clock generation circuit operates in a STANDBY mode as well as conventional OFF and ON modes. In STANDBY mode, a small pre-bias current is applied to amplifiers in the clock generation circuit, which bias voltages on internal nodes to very near their operating voltage values. This reduces transient perturbations on signals as the clock generation circuit is returned to ON mode. The smaller transients settle faster, and allow the clock generation circuit to achieve very fast startup times from STANDBY to ON. The very fast startup times allow the clock generation circuit to be placed in STANDBY mode more often, such as when a system must monitor and rapidly respond to activity on an external bus or interface (such as an RF modem).