The effect of open-loop gain on the radiated emissions from the power-supply lead of an oscillator

The effect of open-loop gain on the spectrum of the supply current drawn by a feedback oscillator is analyzed numerically using a simple harmonic balance technique to determine the steady-state waveforms. It is demonstrated that boosting the open-loop gain increases the spectral bandwidth occupied by the power-supply current. An oscillator must be designed to have sufficient small-signal open-loop gain at the fundamental frequency to ensure reliable oscillation under worst-case conditions and to achieve any noise or time-jitter requirements. However, an unnecessarily large open-loop gain increases the possibility of excessive radiated emissions from the power-supply lead of the circuit and raises the demands on the supply-lead filtering when the circuit is installed in a system.<
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