| 摘要 |
An automatic bias control ("ABC") circuit reduces the source current, e.g., collector-bias current, drawn by a power amplifier in order to minimize power consumption, without significantly affecting the amplifier's gain. The ABC circuit accomplishes this by regulating the control current supplied to a power amplifier in response to a sensor signal indicative of the amplitude of the source signal and a computercontrolled reference signal. The invention can be practiced advantageously in a terminal amplifier of a transmitter of a dual-mode mobile cellular radio-telephone. The sensor signal is used to take into account variations in the collector-bias current required to achieve a pre-determined amplifier gain under, for example, changing ambient (e.g., temperature) conditions. The reference signal is used to indicate, e.g., the mode of operation of the radio-telephone (i.e., whether digital or analog), the mode of operation of the amplifier (i.e., whether linear or non-linear), and the power level of the radio-frequency signal being supplied to the power amplifier. Accordingly, in each case, the bias currents can be set to lower values than in conventional linear amplifiers used in digital radio-telephones or non-linear amplifiers used in analog radio-telephones operating under the same conditions, thereby reducing power consumption.
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