| 摘要 |
In an amplifier comprising an FET (11) having a gate electrode and source and drain electrodes and a drain bias circuit (19) controlled by an output power control command to supply a drain bias to the drain electrode, a gate bias circuit (17) is controlled by the output power control command to supply the gate electrode with a controlled voltage as a gate bias, The gate bias circuit may have a voltage source terminal (25) given a predetermined voltage and comprises a gate bias control device (27) for controlling the predetermined voltage into the controlled voltage in accordance with the output power control command, Preferably, the device comprises an ROM for memorizing gate voltage data and a voltage producing section for converting the predetermined voltage to the controlled voltage in compliance with one of the gate voltage data that is selected by the command, Alternatively, the device comprises a voltage divider for dividing the predetermined voltage into divided voltages and a selector for selecting one of the divided voltages as the controlled voltage in accordance with the command,
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