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HF Vacuum-Tube-Amplifier Parasitic Oscillations

February 22nd Fact-of-the-Day

Vacuum-tube-amplifier parasitic oscillations can be classed into dynatron, low-frequency, and high-frequency types, where low-frequency refers to oscillations below the frequency of operation and high-frequency refers to oscillations above that frequency. High frequency parasitic oscillations usually result from the inductance of the lead between the grid and an input tuned circuit and the inductance of the lead between the plate and an output tuned circuit resonating with tube interelectrode capacitances and/or neutralizing capacitors at the high oscillating frequency. At a high oscillation frequency the normal input and output circuit tuning capacitors usually have low enough reactances that they can be considered as essentially short-circuit connections that effectively ground one side of the grid and plate parasitic resonant circuits. ©2005 Martek International All rights reserved.


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