| 摘要 |
In a communications system, a power amplifier is dynamically biased in response to a control signal indicative of the required transmission power. In delivering relatively high transmission power, the DC operating point of an amplifying element in the power amplifier is placed far from the cutoff and saturation regions of the output characteristics of the amplifying element. As a result, the corresponding input signal at a high drive level to the power amplifier is virtually undistorted thereby and, at the same time, a high power efficiency is achieved. In delivering relatively low transmission power, although the DC operating point is placed relatively close to the cutoff region of the output characteristics of the amplifying element, because of the corresponding input signal which is at a low drive level, the power amplifier minimally distorts the input signal. However, a high power efficiency is maintained because the input DC power to the power amplifier is reduced as well as the transmission power.
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