| 摘要 |
PURPOSE:To decrease a voltage gain without spoiling stability, by providing a variable resistance element in the path between the output and input of an amplifier and by further providing another variable resistance element between the input and a reference potential. CONSTITUTION:Resistance Rf is connected across amplifier 1. Then, the 1st variable resistance element 2 is connected between one terminal of capacitor C1 connected at the other terminal to the input terminal of amplifier 1 and the output terminal of amplifier 1. Further, the 2nd variable resistance element 3 is connected between said terminal of capacitor C1 and the reference potential. Variable resistance elements 2 and 3 are composed of diodes D1 and D2, and D3 respectively and their resistance values are controlled by current sources 4 and 5. Consequently, even if the variable resistance values of variable resistance elements 2 and 3 are decreased, the loop gain is suppressed to a constant value, so it will never near the amplification factor of amplifier 1, so that the voltage gain can be decreased without spoiling the stability. |
