| 摘要 |
PURPOSE:To attain multiple-stage connection of a directly coupled broad band and high gain amplifiers by synthesizing an output signal and a signal with only a low frequency component existed therein through a differential input circuit, thereby eliminating a DC bias voltage to be included in an output signal. CONSTITUTION:A signal outputted from an amplifier 12 includes a DC bias voltage. The signal is divided into one path through which the signal is fed to a transistor(TR) 14 and the other path through which a signal with only a low frequency component including the offset of the DC voltage extracted therefrom by a voltage follower circuit comprising an operational amplifier 19, and a low pass filter is inputted to a TR 15, and the signals of each path are synthesized by the differential input circuit comprising the TRs 14, 15. Since amplifiers are to be coupled directly, a capacitor inserted between amplifiers is not required and an amplifier circuit ensuring the gain from over a frequency sufficiently lower than a conventional low frequency is obtained.
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