| 摘要 |
PURPOSE:To perform widely dynamic signal intensity display, by using an external control signal controlling an output of an amplifier in which the gain is stepwise changed, to a prescribed range, as a part of an intensity display signal of the signal inputted to the amplifier. CONSTITUTION:A variable gain amplifier 10 independent of a signal line of a tuner has five stages of gain such as 0, 20, 40, 60 and 80 dB by a control circuit 40. A signal representing the intensity is inputted to a window comparator 30 via said amplifier 10 and a detection circuit 20. The gain of the amplifier 10 is controlled so that the detected output G via the amplifier 10 is within a V1 and a V2 with the output of said comparator 30. The detected output G and gain controlling signals A-D from the control circuit 40 are added at an addition circuit 50 and displayed as the signal intensity in a meter 8. This signal is proportional to the logarithm of the input signal level, allowing to display the intensity of signal of high accuracy and high dynamic range. |
