| 摘要 |
PURPOSE:To realize a highly accrate constant current circuit, by connecting a constant voltage element between the base and the collector of a transistor for setting the reference current and connecting a resistance to the constant current supplying transistors except a specific one. CONSTITUTION:The voltage drop caused by a constant voltage element 10 which is connected between the base and the collector of a reference transistor TR1 is referred to as VC. Thus the reference current IREF is set as IREF=(VCC-VBE1- VC)/R1. The constant current supplying TR 2 and 3 mirror the current IREF and supply the corrector currents I2, I3... to other circuit parts. If the TR3, for example, among the TR 2, 3... supplyies the highest potential VMAX for its collector voltage, the element 10 is selected so that the collctor voltage of the TR1 is set to VMAX. At the same time, a resistance 12 is connected to the collector of the TR2, and the constant current is supplied through the resistance 12. With such a circuit, the collector voltage is equal to each other among the TRs. Thus a circuit having high accuracy can be obtained without receiving an early effect. |
