| 摘要 |
PURPOSE:To cause the potential across the resistance via the current of the constant current circuit by installing the constant current circuit which flows the current equivalent to the collector current of the input transistor, thus securing the input offset voltage of the zero level by the potential. CONSTITUTION:The input signal applied to the base of transistor Q1 causes voltage VR1 across resistance R1 when the DC amplification factor of Q1 is set to hFE1. Here if the collector resistance is set as R3=R4=R5, the collector current becomes identical among transistors Q1, Q2 and Q3 each. As a result, the voltage becomes VR across resistance R. As the input offset voltage is VR1-VR, it can be made zero regardless of the power voltage under the conditions of resistance R=R1/hFE1. Furthermore, base resistance R2 of transistor Q2 is made small extremely, and thus the voltage at both ends is always kept about zero. Thus the steady operation is secured for the differential amplifier circuit. |
