A 2.7-V SiGe HBT variable gain amplifier for CDMA applications

A monolithic SiGe HBT variable gain amplifier with high dB-linear gain control and high linearity has been developed for CDMA applications. The VGA achieves a 30-dB dynamic gain control with a control range of 0-2.7 Vdc in 824-849 MHz band. The maximum gain and attenuation are 23 dB and 7 dB, respectively. Input/output VSWRs keep low and constant despite change in the gain-control voltage. At a low operation voltage of 2.7 V, the VGA produces a 1-dB compression output power of 13 dBm and +885-kHz ACPR of -57 dBc at a 5-dBm output power.