| 摘要 |
PURPOSE:To make the logarithmic change of gain linear for the change of a feedback quantity by providing gain control circuit, which changes the feedback quantity to control gain, and mixers in the output and the input and connecting the input-side mixer and the gain control circuit through a resistance. CONSTITUTION:The output of gain control circuit 1 of feedback quantity x becomes xX for the input of state variable X. Output signal xX of circuit 1 and input signal ei are mixed by first mixer circuit 2, and the output is inputted to not only circuit 1 through resistance Ro but also second mixer circuit 3. In circuit 3, output xX of circuit 1 and output X=ei+xX of circuit 2 are mixed to output voltage eo=ei(1+x)/(1-x). When logarithms of gain G=eo/ei of this circuit are subjected to progression expansion to take up to the first term, lnG 2x is true approximately; however, the approximate error caused by the second term and succeeding terms removed in progression expansion is corrected by adjusting resistance Ro, and the relation between gain of the feedback and logarithms becomes linear. A linear attenuation logarithmic characteristic can be obtained for the feedback quantity by providing a phase switching circuit in the output of circuit 2. |
