| 摘要 |
A current switching circuit has a setting section (2), a switching section (3) and a switch changeover section (4). The switching section (3) has a current mirror circuit, n switching transistors (TrSW1-TrSWn), and a compensating circuit. The current mirror circuit has first through third transistors (Tr1-Tr3). Emitters of the first and second transistors are connected to a power supply terminal (1) and bases thereof are connected with each other. The third transistor (Tr3) has an emitter connected to the bases of the first and second transistors (Tr1,Tr2), a collector grounded, and a base connected to a collector of the first transistor. The switching transistors (TrSW1-TrSWn) have emitters connected to the collector of the second transistor (Tr2), and collectors connected to one terminals of n load elements (Z1-Zn). The other terminals of the load elements are grounded. The switch changeover section (4) controls the base currents of the switching transistors (TrSW1-TrSWn). The compensating circuit comprises two compensating transistors (TrA,TrB). The first compensating transistor (TrA) has an emitter and a base connected to an emitter and a base of the second transistor (Tr2), respectively. The first compensating transistor (TrA) has a same size as that of the second transistor (Tr2). The second compensating transistor (TrB) has an emitter connected to a collector of the first compensating transistor (TrA), a collector grounded, and a base connected to the collector of the second transistor (Tr2). The second compensating transistor (TrB) has a same size as that of each of the n switching transistors (TrSW1-TrSWn). <IMAGE> |
