A low current CMOS voltage regulator including RF desensitization for RFIC power amplifiers

This paper presents a CMOS voltage regulator employing an operational-amplifier operated from a 1.8V supply with very low current consumption, capable of delivering a stable regulated 1.4V output voltage with high enough current sourcing capability for the biasing of GaAs HBT RFIC power amplifiers, and subjected to strong RF perturbations. These features are particularly important in multi-technology RFIC power amplifier modules requiring advanced CMOS control functions for efficiency and linearity performance improvement, but having minimal RF signal isolation between the RF amplifier IC and the CMOS control IC, for compactness and cost considerations. The regulator design uses a recycled folded cascode operational-amplifier structure in a CMOS 0.18μm technology. The results presented show a total bias current of 135μA for the operational-amplifier, a current sourcing capability of 20mA when delivered to the equivalent load seen at the base of a power GaAs HBT RF transistor under 1.88GHz-20dBm excitation, and a drop of only 40mV in the regulated output voltage (97% regulation) when using an RF isolation inductor as small as 6nH.