| 摘要 |
A radio frequency (RF) amplifier for amplifying an RF signal with a high power efficiency and with a minimum of signal distortions by using a GaAs field effect transistor (FET). An idling current for class "A" amplification is set in the FET. An output low pass filter is connected to the drain of the FET and provided with an impedance higher than a high gain impedance, so that the FET and a load may be matched in power during high RF signal operation, i.e., the dynamic impedance of the FET and the impedance of the load may be matched. A drain bias to the FET is turned on and turned off in synchronism with the ON/OFF of the input RF signal. The amplifier, therefore, not only performs class "A" amplification with a minimum of signal distortions but also further saves power since it is turned off in the absence of a signal, thereby achieving a higher power efficiency.
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