Oscillator with feedback amplifier and resonance circuit - has crystal-driven resonance chain controlling input impedance to ensure stability

摘要

The amplifier (1) input (4a,4b) is provided by a series resonance chain consisting of an inductor (6), capacitor (7) and resistor (8). The amplifier outputs (5a,5b) provide negative feedback to the resonance chain. One feedback loop cotnains a non-linear component to prevent saturation of the amplifier. When the input reactance of the amplifier reaches zero and the input impedance becomes less in negative value than the value of the oscillator resistance (8), oscillation occurs at a frequency determined by 1/LC. As a result of this negative feedback the oscillator maintains its frequency irrespective of external loading.