| 摘要 |
PROBLEM TO BE SOLVED: To provide a CATV tuner which is miniaturized, reduces power consumption and is inexpensive while showing satisfactory input return loss characteristics at the time of power source OFF. SOLUTION: A switch circuit 28 is provided between a band-pass filter 22 and an RF amplifier circuit 23, and a load path switched from a tuner input terminal 21 at the time of power source OFF is switched to a path through a capacitor C1 for DC cut and a resistor R1 for impedance matching to the ground. This switch circuit 28 has a depressed p-channel single gate FET 29 and when a power source is turned off, the FET 29 is turned on and switches a load path to the path through C1 and R1 to the ground. Thus, satisfactory input return loss characteristics are provided at the time of power source OFF. Besides, since the switch circuit 28 is composed of only the FET 29 and resistors R2 -R4 , the tuner can be formed while being miniaturized, reducing power consumption and becoming inexpensive.
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