| 摘要 |
PROBLEM TO BE SOLVED: To obtain a gain controller with less power consumption, ease of miniaturizing and suitable for circuit integration that can keep a shift in a passing phase nearly constant over a gain variable range. SOLUTION: The gain controller is provided with a cascode amplifier circuit consisting of a 1st field effect transistor TR1 of common source connection and of a 2nd field effect transistor TR2 whose source is connected to a drain of the 1st field effect transistor TR1 and whose gate receives a gain control signal, with an input matching circuit Min that is connected between an input terminal of a high frequency input signal and the gate of the 1st field effect transistor TR1 and can realize an impedance at which the gain is maximized, and with an output matching circuit Mph that is connected between the drain of the 2nd field effect transistor TR2 and an output signal of a high frequency output signal and provides an impedance when viewed from the drain of the 2nd field effect transistor TR2 to have a value by which a phase shift of the passing high frequency signal is nearly made constant within a variable voltage range of the gain control signal.
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