| 摘要 |
The present invention describes a voltage controlled attenuator (VCA) to control an output power level of a radio frequency (RF) signal and to direct the RF signal to an appropriate path for a multi-mode and multi-band radiotelephone without using an external switch and without using multiple common VCAs. The present invention comprises a single differential amplifier (202) and a plurality of steering blocks (204, 206, 208, 210) with each of steering blocks having a path dedicated to a specific RF band and a specific RF mode, having a pair of steering lines (252, 254, 256, 258, 260, 262, 264, 268) to control the RF signal level by having a differential voltage applied, and being capable of being disabled by having its steering lines grounded.
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