| 摘要 |
PURPOSE:To obtain a differential input circuit constituting an operational amplifier of high oscillation stability by shunting a part of the collector current of the transistor TR of a differential input stage to a fixed voltage source. CONSTITUTION:When a differential input voltage (Vid=ViN+-ViN-) is generated in the input, a collector current difference DELTAIc (=Ic1-Ic2) between TRs Q3 and Q4 is generated by the TR operation in accordance with a formula 1. In this case, I3=I4 is true and a collector shunt ratio of TRs Q3 and Q4 is set to one. Consequently, Ic1=Ic2=2I3 is true. Since this current output is shunt by TRs Q3 and Q4 and a current IOUT=DELTAIc/2 flows to the output as the result, a conversion conductance gm of the differential input circuit is given in accordance with a formula 2. This conversion conductance is reduced to a half of that of a conventional differential input circuit, and the conversion conductance gm can be reduced without reducing the bias current of the differential input stage.
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