| 摘要 |
PURPOSE:To reduce an effect of the DC drift, by controlling the gain of the 1st amplifier and at the same time feeding negatively the DC output level of the output of the 1st amplifier back to the input side as well as to the 2nd amplifier. CONSTITUTION:It is possible to control the gain of the 1st amplifier consisting of a direct-coupled 2-stage amplifier of an emitter earth circuit 2B and an emitter follower circuit 3B. At the same time, the DC output level of the 1st amplifier is negatively fed back to the input side. This DC output level is divided and fed negatively back to the input side of the 2nd amplifier consisting of a direct-coupled 2-stage amplifier of an emitter earth circuit 6B and an emitter follower circuit 7B. As a result, the same DC operation conditions are secured for the collector current, etc. and the gain can be controlled to the same level between the 1st and 2nd amplifiers. At the same time, it is possible to reduce an effect of the voltage drift between the base and the emitter of transistors Q1- Q4. |
