| 摘要 |
PURPOSE:To control independently a gain and an offset stably by using the 1st difference signal so as to control the offset of a gain variable amplifier and using the 3rd difference signal to control the gain of the gain variable amplifier. CONSTITUTION:The titled circuit consists of a differential amplifier 13 detecting a difference signal between output signals 2, 3, a differential amplifier 14 detecting a difference signal between an output signal of the differential amplifier 13 and a preset reference voltage and a differential amplifier 15 detecting a difference signal between the output signals 2, 4. In detecting a minimum value V1, a maximum value V2 of a positive phase output and a maximum value V3 of a negative phase output, in total three outputs, the differential amplifier 15 operates equations of A=V3-V2=DELTAa and B=V2-V1=b+DELTAb to generate the signal A, which is fed back to an input terminal of a gain variable amplifier 1 and only the offset voltage is controlled in a feedback control system with A=DELTAa 0. Then the differential amplifier 13 generates the signal B, the differential amplifier 14 forms a (B-b) signal and the gain control error is suppressed independently in a feedback control system with B-b=DELTAb 0. Thus, the gain and the offset of the gain variable amplifier are controlled independently and stably. |
