| 摘要 |
Of a first and a second PNP transistor (T1; T2) having commoned base electrodes, the emitters are connected through resistors (R1; R2) to the positive supply voltage terminal (2). The collector lead of the first transistor (T1) includes a current source (3), which supplies a current which is reproduced at the output terminal (4). The commoned base electrodes are driven by a third transistor (T5) connected as an emitter follower, its emitter lead including a current source (5). The base of the third transistor (T5) is connected through a resistor (R5) to the positive supply voltage terminal (2) as a result of which supply voltage variations appear also at the commoned bases of the first and second transistors (T1; T2) so that the output current at the output terminal (4) is substantially independent of supply voltage variations. A differential amplifier comprising fourth and fifth transistors (T6; T7), in which the base of the fourth transistor (T6) is connected to the collector of the first transistor (T1) and the base of the fifth transistor (T7) is connected to a reference voltage (Vref),controls the voltage at the base of the third transistor (T5) so that the collector current of the first transistor (T1) is substantially equal to the current of the current source (3). |
