Abstract: An amplifier circuit unit including a signal amplifying transistor is provided with a first bypass circuit unit for bypassing a part of an input signal to a ground side according to the strength of the input signal, and a second bypass circuit unit for bypassing a part of the input signal to an output side according to the strength of the input signal, whereby gain attenuation control is effected. Also, the amplifier circuit unit is provided with a control circuit unit for decreasing the drain bias current of the signal amplifying transistor when the first bypass circuit unit bypasses the part of the input signal to the ground side, and interrupting the drain bias current of the signal amplifying transistor when the second bypass circuit unit bypasses the part of the input signal to the output side, whereby control of the drain bias current is effected.

Abstract: An amplifier circuit unit including a signal amplifying is provided with a first bypass circuit unit for bypassing a part of an input signal to a ground side according to strength of the input signal, and a second bypass circuit unit for bypassing a part of the input signal to an output side according to the strength of the input signal, whereby gain attenuation control is effected. Also, the amplifier circuit unit is provided with a control circuit unit for decreasing a drain bias current of the signal amplifying when the first bypass circuit unit bypasses the part of the input signal to the ground side, and interrupting the drain bias current of the signal amplifying when the second bypass circuit unit bypasses the part of the input signal to the output side, whereby control of the drain bias current is effected.

Abstract: A ferromagnetic resonance device is disclosed which utilize the perpendicular resonance of ferrimagnetic YIG thin film operable under a D.C. bias magnetic field perpendicular to a major surface of the YIG thin film element. By making the YIG thin film to have a major surface thereof (100) crystal plane of YIG or (111) crystal plane of a substituted YIG having reduced Ku value, lower limit of resonance frequency is extremely lowered. Thus wide range variable filter device can be obtained.