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Author: N.H. Crowhurst

Asymetrical waveforms can cause low-frequency ringing

Another variation of transient distortion occurs with feedback amplifiers. The low-frequency stability, as shown in the Nyquist diagram, may not have sufficient margin. This may not result in oscillation at the low frequency, but gives a peak in the loop gain response (A(3) at a low frequency, such as 1 or 2 cycles. This peak may not show in the overa// response of the amplifier, because the output transformer may produce sufficient loss to offset it. Nevertheless, asymmetrical waveforms (which have the effect of a sudden application of d-c) can cause this peak to give a low-frequency ringing (bounce) of 1 or 2 cycles per second. The bounce itself may not appear in the output, but it can result in quite serious intermodulation because some stages will not amplify uniformly at different parts of this high-amplitude very-low-frequency waveform.

Last Update: 2010-11-03