| 摘要 |
PURPOSE:To expand an equivalent dynamic range to the variation of a signal level by connecting the input of a level sensor to the output or input of the 1st gain control circuit and connecting the output of the level sensor to the 2nd gain control circuit through the 1st gain control circuit and a digital recording/reproducing device or a digital communication equipment. CONSTITUTION:A digital gain control circuit (DGC)1 includes an analog switch (ASW)10 for controlling the gain of an analog switch when a gain control signal (c) consisting of 12 bits is impressed. When all the 12 bits of the signal (c) are low level, all switches of the ASW10 are turned off and the analog signal gain G of the DGC1 becomes the maximum gain GMAX. When an LSb is turned to the high level, the switch on the LSb side is turned on and a resistor 2048R is inputted to a negative feedback loop in parallel, so that the synthetic feedback resistance is turned to 1/2 and the analog signal gain G becomes 1/2 of the maximum gain GMAX. When the bit successive to the LSb is also applied to the negative feedback loop and the analog signal gain G becomes 1/4 of the maximum gain GMAX. |
