| 摘要 |
PURPOSE:To provide the variable gain wide band amplifier which makes precise gain control possible and is provided with wide band characteristics. CONSTITUTION:This device is provided with an amplifier circuit composed of a transistor Q1 which base is connected to an input signal, transistor Q2 which connects the base to a fixed power source, connects the collector to the positive power supply side and extracts an output signal from this side, and transistor Q3 which connects the collector to the emitter of the transistor Q2, connects the base to an AGC voltage and connects the emitter to the collector of the transistor Q1, transistor Q4 which connects the collector to the positive power source, connects the base to the fixed power source and connects the emitter to the collector of the transistor Q1, transistor Q5 which connects the collector to the emitter of the transistor Q2 and connects the base to the base of the transistor Q1, and constant current source 1 connected between the emitter of the transistor Q5 and a ground so as to control a current corresponding to the DC current value of the transistor Q4. |
