A soft-slope output power control circuit for RF power amplifiers

This paper presents an output power control circuit for DCS power amplifiers. The proposed topology allows a power control function to be achieved by varying the power amplifier quiescent current through an external voltage. A soft control slope is attained by exploiting a temperature-compensated exponential control law for the quiescent current. A DCS power amplifier was fabricated in low-cost silicon bipolar technology. It delivers a 33.5-dBm saturated output power with 46% maximum power-added efficiency and 36-dB gain at a nominal 3.5-V supply voltage. An output power control range larger than 40 dB is achieved with a power control slope lower than 80 dB/V.