| 摘要 |
PURPOSE:To decrease much the difference between a reference current and an output current by inserting an operational amplifier between the 1st transistor (TR) and the 2nd TR and impressing a voltage to the control electrode of the 2nd TR by the operational amplifier. CONSTITUTION:Since an input terminal + of the operational amplifier 4 is at a high impedance, almost no reference current I1 flows to the input terminal + of the operational amplifier 4, and then the reference current I1 is the sum of a base current IB and a collector current IC of the 1st TR 2, that is, IB+IC. On the other hand, a voltage equal to a base voltage of the 1st TR 2 is impressed to a base 3b of the 2nd TR 3 by the operational amplifier 4, then an output current I2 becomes a current equal to the collector current IC of the 1st TR 2. Thus, the difference between the reference current and the output current is IB to obtain a current mirror circuit with high accuracy. |
