| 摘要 |
PURPOSE:To reduce the battery power consumption and to inexpensively make a device small-sized and lightweight by changing the gate bias voltage of an FET in accordance with the magnitude of an input or output signal and amplifying a signal having a long amplitude without distortion and reducing an average current. CONSTITUTION:In an IC 50 for power amplification, a dual gate FET Q1 and single gate FETs Q2 and Q3 are used as the variable amplifier in the initial stage and power amplifiers in next and final stages respectively to subject the wave to be modulated of an input terminal 51 to power amplification. At this time, resistors R6 and R7 divide a never control voltage Vc to apply it to a second gate G2 of the FET Q1, and resistors R8 to R10 apply bias voltages Vg1 and Vg2 to gates of FETs Q1 to Q3. Since the voltage Vg1 is a fixed voltage and the voltage Vg2 is obtained by dividing the voltage Vc, the voltage Vg2 of the FET Q3 is raised/reduced in accordance with increase/reduction of the degree of amplification of the FET Q1. Thus, the signal having a long amplitude is amplified without distortion, and the average current is reduced, and the battery is miniaturized, and the device is inexpensively made small-sized and light-weight. |
