| 摘要 |
PURPOSE: An RF switch is provided to control power of an amplifier included in the RF switch using a schmitt trigger circuit to improve the performance of a receiver for weak signals, intensive signals and overload. CONSTITUTION: An RF switch receives an output voltage of an RF automatic gain controller of a tuner as an input of a schmitt trigger circuit(405) to control power of an amplifier(402) included in the RF switch. When a weak signal is received, the RF switch powers on the amplifier to amplify an RF signal. When an intensive signal is received, the RF switch powers off the amplifier to make the amplifier serve as an attenuator so that a range of intensity of received signal is widened. Upper and lower critical values of the operation of the schmitt trigger circuit are decided using the output voltage of the RF automatic gain controller. The response speed of the circuit of controlling the power of the amplifier is lower than the response speed of the RF automatic gain controller of the tuner.
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