Abstract: A crystal oscillator clock circuit which facilitates switching its output between an internally generated clock signal and an externally generated clock signal. A feedback loop detects the presence of an externally generated clock signal applied to an output pin of a crystal oscillator circuit and powers down the internally generated clock signal. As a result, the crystal oscillator clock circuit simply passes the externally generated clock signal as its output signal.

Abstract: A wideband tuneable low noise amplifier that is capable of receiving signals over a wide range of frequencies, providing tuneable filtering to remove out of band interferer signals, and providing variable gain for a wide range of frequencies. To accommodate variable gain, the low noise amplifier has an amplifier stage comprising two gain stages, and the relationship between the gain stages is controlled responsive to changes in the voltage gain of an input stage. Linearity monitoring combined with Q-enhance may be employed to increase performance at low signal levels.