A bias boosting technique for a 3.2V, 1.9GHz Class AB RF amplifier designed in a 30GHz BiCMOS process is presented in this paper. In a Class AB amplifier, the average current drawn from the supply depends on the input signal level. As the output power increases so does the average currents in both the emitter and the base of the power transistor. The increased average current causes an increased voltage drop in the biasing circuitry and the ballast resistor. This reduces the conduction angle in the amplifier, pushing it deep into Class B and even Class C operation, reducing the maximum output power by 25%. To avoid the power reduction, the amplifier should have a larger bias which inevitably has a larger power dissipation at low output power levels. The proposed bias boosting circuitry dynamically increases the bias of the power transistor as the output power increases. The amplifier has less power dissipation at low power levels with an increased maximum output power.
本文介绍了一种采用30GHz BiCMOS工艺设计的3.2V,1.9GHz AB类RF放大器的偏置升压技术。在AB类放大器中,从电源汲取的平均电流取决于输入信号电平。随着输出功率的增加,功率晶体管的发射极和基极中的平均电流也会增加。增加的平均电流会导致偏置电路和镇流电阻中的压降增加。这样可以减小放大器的导通角,使其深入到B级甚至C级工作,最大输出功率降低了25%。为避免功耗降低,放大器应具有较大的偏置,在低输出功率水平下不可避免地具有较大的功耗。提出的偏置升压电路随着输出功率的增加而动态地增加功率晶体管的偏置。该放大器在低功率水平下具有更低的功耗,并具有最大的输出功率。 P>
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