| 摘要 |
PURPOSE:To obtain an inexpensive amplifier possible for miniaturization by providing an AGC circuit to an amplifier of a television common viewing system so as to allow multi-channel television signals to be detected altogether by a detection circuit. CONSTITUTION:When a television signal is inputted to an input terminal (a), after said television signal passes through an AGC element 1 and is amplified by an amplifier circuit 2, the result is fed respectively to an output terminal (b) and the AGC circuit 4. The television signal fed to the AGC circuit 4 is converted into a DC signal by a detection circuit 5 and amplified by a DC amplifier circuit 6, then given to a comparator circuit 7. The comparator circuit 7 compares the DC signal with a preset reference level, and a deviation is caused and it is fed to the AGC element 1 as a control signal, and for example, when the DC signal is higher than the reference level, the high frequency resistance of the AGC element 1 is increased and when the level is lower than the reference level conversely, the high frequency resistor is reduced so as to obtain a constant output at all times at the output terminal (b).
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