| 摘要 |
<p>RCA 73,301 The outputs of a pair of non-additive combiners are coupled to respective inputs of a differential amplifier and an a.c. signal to be amplified is applied to a selected input of one of the combiners. A control circuit operates in a first mode to apply control voltages to the combiner inputs for causing the one combiner to block the a.c. signal and also causing both combiners to apply a common mode input voltage of a first value to the amplifier inputs. In a second mode, the control circuit changes the values of the control voltages in a sense to cause the one combiner to pass the a.c. signal and to also cause both combiners to apply a common mode input voltage of a second value to the amplifier inputs whereby, in either mode, the amplifier produces a constant quiescent d.c. output voltage.</p> |
