IMPEDANCE INVERSION TECHNIQUE PREVENTING OSCILLATOR SATURATION
Original Publication Date: 1987-Oct-01
Included in the Prior Art Database: 2001-Oct-22
When a conventional, common base Colpitts oscillator (Figure IA) is subjected to low supply voltage, the sustaining amplifier can be sent into saturation due to excessive feedback from the oscillator tank. Such satura- tion seriously loads down the resonanting tank and degrades the tank Q factor. Moreover, the input resistance of the amplifier(transistor) may be so low that it loads down the resonating tank. The oscillator sideband noise ratio is a function of the tank power and the tank Q factor. Degradation in either of these factors likewise degrades the sideband noise ratio. This invention provides a solution to these deficiencies by employing an impedance inversion technique. With such improvements, the oscillator is able to perform at a higher sideband noise ratio.