| 摘要 |
PURPOSE:To realize the muting by obtaining the DC output according to the input IF level through extraction of the output in a proper combination from several steps of the IF amplifier, thus eliminating the unpleasant hearing due to the repetition of the field fluctuation. CONSTITUTION:If the input to transistor 8 is over the intermediate level, it is applied to transistor 9 as voltage Vm. While adjustable voltage Vc is applied to transistor 10 via volume 11. Here if the state of Vm<Vc is set as the intermediate input, transistors 9 and 10 are turned off and on each. Accordingly, transistors 12 and 15 are on with transistors 13 and 14 turned off respectively. In this instant, transistor 19 is turned on and DC cuurent IB flows. At the same time, current IA flows to transistor 20. After this, IA flows to transistors 15-17 to emerge at output terminal 21 through transistor 18 in the form of the voltage. Then when the base voltage of transistor 9 is identical to VC, transistors 12-15 are at the active region. And the current of IA/2+IB/2 flows to transistors 16 and 17, and the rest current flows to the power source. |
