| 摘要 |
In a power amplifier including a power output stage connectable to a load having a minimum rated impedance, there is disclosed means for driving the power output stage so as to prevent excess power dissipation thereby caused by loads having impedances lower than the minimum rated impedance. A capacitor is utilized to establish a desired voltage level for an amplification stage which provides the current for the power output stage, the maximum current being determined by the voltage level on the capacitor. Means are provided for charging the capacitor to the desired voltage level, the charging means being incapable of maintaining the desired voltage level on the capacitor in the presence of currents from the amplification stage at or near the maximum desired output current. A portion of the output of the power output stage is fed back to the capacitor to maintain the charge thereon at the desired voltage level; however, this is only operative when the impedance of the load is equal to or greater than the rated minimum impedance so that in the event of lower impedances, the charge on the capacitor is not maintained, reducing the current limit from the amplification stage.
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