| 摘要 |
PURPOSE:To eliminate the need to compensate frequency characteristics by performing multistage connection while regarding one unit a two-stage variable gain amplifier which has high input impedance and low output impedance. CONSTITUTION:A signal inputted to a common collector PNP transistor (TR) 14 is outputted from a common emitter NPNTR15. A variable attenuating element 18 is provided to the emitter of the PNPTR14 to control a gain. Amplifiers 26 each composed of the TRs 14 and 15 as one unit are connected into multistage constitution with a prescribed gain. In this case, the influences of floating capacitor Cs and parasitic inductance Ls generated between the stages are reduced remarkably by high-input and low-output impedance characteristics. Consequently, a phase compensating circuit is unnecessary. |
