| 摘要 |
The present invention provides a feed-forward amplifier having a predistortion circuit to provide a sufficient compensation for a variation in temperature. When a predistortion circuit 3 is used to minimize distortion in a main amplifier 6, the circuit 3, a variable attenuator 4, a variable phase shifter 5, and a main amplifier 6 are located in this order and a control circuit 19 controls the variable attenuator 4 and variable phase shifter 5 so that a carrier component, that is, an input signal, in a detected distortion component decreases to a minimum. In this manner, when the gain of the main amplifier 6 varies due to a variation in temperature, the preceding variable attenuator 4 and variable phase shifter 5 compensate for the variation of the gain. The input level of the predistortion circuit 3, however, is not affected, so the relationship between output levels of the predistortion circuit 3 and main amplifier 6 remain unchanged compared to the amount prior to the temperature variation, thereby providing the same compensation effect.
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