Design and Characterization of a 1-Watt Driver Amplifier for Wireless Infrastructure

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  • Author: Chin-Leong Lim
Variable gain amplifiers (VGA) find application in RF systems that require an amplified signal level to be instantly adjusted in reaction to a continuously changing operating environment. Transmitters may require that the gain in the driver stage be made variable to conserve power under good propagation condition or to minimize interference to adjacent sites. In receivers, particularly for cellular base-station service, the gain of the 2nd/3rd stage LNA is made variable to prevent overloading of the subsequent stage (mixer in the superhet or DAC in direct conversion receiver) under strong signal condition. In a tower mounted LNA, a relatively large output power is also needed to overcome losses in the long run of coaxial cable linking it to the radio shelter at ground-level.