METHOD TO SHORTEN CRYSTAL OSCILLATOR´S STARTUP TIME

摘要

An oscillator circuit includes an amplifier including at least two terminals for receiving a crystal and an automatic amplitude control loop coupled to the amplifier including biasing circuitry switched between a first operational mode and a second operational mode. The first operational mode occurs during an initial time period and the second operational mode occurs after the initial time period is expired. The biasing circuitry includes first and second PMOS transistor circuits, each transistor circuit including an unswitched PMOS transistor and a switched PMOS transistor. Alternatively, the biasing circuitry can include first and second NMOS transistor circuits, each transistor circuit including an unswitched NMOS transistor and a switched NMOS transistor. The biasing circuitry is under control of an internally generated control signal.