| 摘要 |
PROBLEM TO BE SOLVED: To achieve a high speed operation and low noise in an amplifier circuit which amplifies an electric signal by using a base-grounded transistor.SOLUTION: An amplifier circuit 12 includes: a base-grounded first transistor 23 whose emitter currents vary in accordance with variations in input currents to be input to an emitter; a base-grounded second transistor 24 whose emitter is connected to the collector of the first transistor 23, and whose collector voltage varies in accordance with variations in the emitter currents of the first transistor 23; a collector-grounded third transistor 31 whose base is connected to the collector of the second transistor 24; and an amplification part 40 for receiving the emitter voltage of the third transistor 31, and for outputting an amplified voltage obtained by amplifying the emitter voltage of the third transistor 31, therein the base resistance of the second transistor 24 is larger than the base resistance of the first transistor 23.SELECTED DRAWING: Figure 2 |
