| 摘要 |
<p>PURPOSE: To provide an amplifier serving for both transmission and reception stably operated in both transmission mode and reception mode with simple circuit constitution by performing feedback from a feedback circuit provided with a feedback resistor whose resistance value is variable and a second active element for the feedback to a first active element for amplification. CONSTITUTION: The feedback from the feedback circuit provided with the feedback resistor R2 whose resistance value is variable and the second active element (FET2) for the feedback is performed to the first active element (FET1) for the amplification. For instance, a resistor is inserted between the drain of the FET1 for the amplification and the gate of the FET2, the feedback is performed by the resistor, gate bias is linked also with a feedback resistor part, a feedback amount is controlled and coping is performed at the time of the reception and at the time of the transmission. That is, at the time of the reception (when the gate bias is deep), the value of the feedback resistor is made large, the feedback amount to the FET1 is reduced and largest possible gain is obtained. At the time of the transmission, the resistance value is made small, the feedback amount is increased and the gain is stabilized small.</p> |
