| 摘要 |
PURPOSE:To form a constant resistance circuit having various output voltage versus current characteristics through the change in a resistance value only by providing two bipolar transistors(TR), connecting the collector of a 1st TR via a reverse voltage preventing rectifier to a 1st input/output terminal and connecting the base and emitter to a 2nd TR directly. CONSTITUTION:A voltage between input/output terminals 1, 2, that is, an output voltage rises gradually from zero, then a current determined by the combined resistance of resistors 8, 9 flows as a collector current of the TR 4. In this case, an output current flowing to a loop forming circuit 13 increases in proportion to the output voltage and the output voltage versus current characteristic shows a constant resistance characteristic. Moreover, the output voltage rises further, the collector current of the TR 4 is increased and the voltage across the control current setting resistor 8 reaches the base-emitter voltage of the TR 5, then the TR 5 is activated. Then a constant current flows to the base of the TR 4, and even if the output voltage rises further, the collector current of the TR 4 becomes constant. |
