A variable gain amplifier with 50-dB control range for 900-MHz applications

A variable gain amplifier for 900-MHz applications has been designed and fabricated in a BiCMOS process with f_T = 24 GHz. The amplifier has linear-in-dB gain control with a 50-dB control range. The maximum gain is 28 dB and the third-order output intercept point (OIP3) is 13.7 dBm. The gain is achieved in one gain stage with a cascoded output. The amplifier bias network and the gain-control circuitry are temperature compensated for temperature-independent gain at any gain setting. The bias network also uses a feedback loop to cancel out undesired low frequencies present at the radio-frequency input. The maximum output power is +10 dBm and the output 1-dB compression point is +8.7 dBm. Active chip area is 0.1 mm². The amplifier is packaged in a SOT-363 and consumes 30 mA from a 2.8-V supply.