| 摘要 |
PURPOSE:To attain stable input impedance and simplified circuit constitution by providing a buffer circuit and a bias circuit to a signal input section, connecting directly one or >=2 filter circuits and amplifiers to the output of the buffer circuit so as to provide a bias from said bias circuit to the amplifiers. CONSTITUTION:A non-inverting input terminal (+) of a differential amplifier 8 is connected directly to an output of the buffer circuit 42 provided to the signal input section and a bias is given to the differential amplifier 8 from the bias circuit 44 via the buffer circuit 42. The bias circuit 44 consists of resistors 50, 52 and 54 and diodes 60, 62. Then the buffer circuit 42 acts like a conventional buffer circuit in terms of AC, while it functions as a stabilized bias circuit to the differential amplifier 8 in terms of DC through the direct coupling of the differential amplifier 8, thereby increasing the input impedance and stabilizing the bias input. |
