| 摘要 |
A cathode-follower power output stage is driven by a novel drive stage to provide with low distortion the large signal required to drive the output stage. The drive stage comprises two series connected vacuum tubes which share the large static and dynamic voltages of the drive stage so as to provide a drive signal having a large voltage swing, without generating audible distortion and without subjecting the drive stage tubes to excessively high voltages. The plate of a first drive tube is connected to the cathode of the second drive tube. A load impedance is connected from a B+ power supply terminal to the plate of the second drive tube. The grid of the second drive tube is driven by a signal responsive voltage divider network driven by the plate of the second drive tube. The voltage divider network maintains the grid of the second drive tube at a voltage approximately midway between the voltage of the second drive tube plate and the ground as the plate voltage swings in response to the signal current flowing through the load impedance. The two series connected drive tubes thereby share approximately equally both the quiescent static voltage and the dynamic output voltage of the drive stage as the latter drives the grid of the cathode-follower output stage with the required large amplitude voltage swings.
|
