| 摘要 |
PROBLEM TO BE SOLVED: To improve the efficiency of a power amplifier effectively which is provided in communications equipment, etc. SOLUTION: This amplifier circuit is provided with an amplifying element for performing power amplification of an input signal; a detecting means 14 provided at the preceding stage of the amplifying element and for detecting the input signal, a balancing means 15 for balancing the detected output of the detecting means 14 with a prescribed time constant; and a control means 30 for variably setting the bias voltage of the amplifying element, on the basis of the average level of the input signal obtained by the balancing means 15, and which can perform efficient amplification by a bias voltage suitable for input level at that time.
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