| 摘要 |
An amplifier circuit comprising a single ended push-pull amplifying stage comprised of field effect transistors. A pre-amplifier stage formed of a differential amplifier is coupled to the single ended push-pull amplifying stage for supplying a signal thereto. The output terminals of the differential amplifier are connected to the respective gate electrodes of the field effect transistors included in the single ended push-pull amplifying stage, and load impedance means couple the differential amplifier output terminals to the source or drain electrodes of the field effect transistors. A variable current source is connected to the differential amplifier for controlling the current flowing through the differential amplifier as a function of variations in the operating voltage that is supplied to the load connected to the single ended push-pull amplifying stage. Variations in this operating voltage cause corresponding changes in the differential amplifier current to thereby change the bias level of the signal supplied by the differential amplifier to the single ended push-pull amplifying stage so as to maintain the idling currents of the field effect transistors at a substantially constant level, thus preventing the occurrence of cross-over distortion.
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