| 摘要 |
<p>PROBLEM TO BE SOLVED: To have a circuit operate with low current consumption, to reduce the deterioration of input/output reflection characteristic when the gain is variable and to secure stable operation, even in the case of expanding a variable gain width. SOLUTION: A first FET 1 on the side of an input terminal T1 and a second FET 2 on the side of an output terminal T2 are connected to serially share the power source current of a power source terminal T3 , when a ground potential is viewed from the terminal T3 , and to operate by a low current. In addition, a third FET 3 and a resistor 29 provided with a variable resisting function are arranged between the first and second FETs 1 and 2, and a capacitor 32 for grounding by a high frequency is connected between the source/ground potential of this second FET 2. Thus, the deterioration of output reflecting characteristic at gain variation is suppressed. In addition, a fourth FET 4 with the function of a signal attenuator is together provided with bias resistors 33 to 35, to improve the linearity of the inclination of total gain variable characteristic.</p> |
