Low dropout regulator with thin pass device

Abstract

Systems, methods and apparatus for efficient control and biasing of pass devices that include at least one thin pass device and a remaining of thick pass devices. When operated at extreme high and low voltages, the at least one thin pass device maintains operation in its saturation region of operation while the remaining pass devices may be driven into their triode regions of operation. The thin and thick pass devices are arranged in a cascode configuration that includes a plurality of stacked devices. Biasing of the thin and thick cascode devices can be according to a voltage division scheme which protects the devices when the voltage across the stack is high, and provides a skewed voltage division across the stacked devices that promotes a higher gate-to-source voltage of the thick pass devices for a lower R. In one exemplary case, gate length of the at least one thin pass device may be reduced to provide a lower gate-to-source voltage of the thin pass device during operation in the saturation region. An exemplary implementation of an LDO controlling the pass devices for providing RF power to a power amplifier is described.