| 摘要 |
PROBLEM TO BE SOLVED: To reduce the noise output of a high-frequency signal over a wide carrier frequency range by connecting one end of a bypass capacitor to the signal output terminal of an amplifying means and the other end to the common output terminal of the amplifying means, and inserting series resistances between the signal output terminal of the amplifying means and a device output terminal, and the common output terminal of the amplifying means and a device common output terminal. SOLUTION: A capacitor microphone unit 10b has a series resistance 24 inserted between the drain of an FET 19 and a microphone signal output terminal 22. For example, the equivalent series resistance of the bypass capacitor 21 is <=1Ω, so a resonance current between a microphone signal output power transmission line 31 and the bypass capacitor 21 is reducible to 1/10 to 1/100 by setting the series resistance to tens to hundreds ofΩand the high frequency voltage applied to the drain of the FET 19 is also reducible to 1/10 to 1/100. Consequently, noise generated with a high-frequency signal radiated or conducted from the transmission part of a radio device can be suppressed low.
|
