| 摘要 |
PURPOSE:To eliminate an output DC level with a variable gain by connecting collectors of transistors (TRs) having the same current division ratio but opposite phase in 2 sets of differential pairs so as to add a current to the collectors of the TRs having a load resistor. CONSTITUTION:The TRs having the same current division ratio of 2 sets of differential TR pairs controlling the current division ratio of signal currents being in phase and in opposite phase to an input signal are divided into two TRs having a base and an emitter in common, the collectors of the TRs in phase and in opposite phase to the divided TRs are connected and the connected point is connected to collectors of the TRs of the different current ratio so as to cancel the inverting/noninverting complementary AC signal and the result is added to a DC current of the TRs of the different current division ratio. That is, TRs 3, 8 are connected in common to a terminal VAGC in the 2nd and 3rd TRs controlling the gain and TRs 4, 5, 6, 7 are connected in common to a terminal Vref thereby sharing respective bases and emitters in common.
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