Low-dropout voltage reference: An approach to buffered architectures with low sensitivity

A modified circuit topology for bandgap references capable of providing very high load current with output which has small sensitivity against temperature variations is presented. Employing a proportional-to-absolute-temperature (PTAT) current source and a complementary-to-absolute-temperature (CTAT) voltage source in a novel closed-loop configuration, the output voltage can be tuned over a wide range of voltages lower or higher than Silicon bandgap voltage of 1.2 V. These features make the configuration a promising competitor for low-dropout regulators. Low-power and low-voltage design considerations of the circuit offering many advantages are addressed. With different specifications, two design examples in 0.18-yKm standard CMOS technology are reported. Thanks to a modified amplifier topology, the 0.9 V and 1.3 V bandgap references have fast stable operation for the load currents ranging from 0 mA to 100 mA with load capacitors as low as 10 pF and no equivalent series resistance (ESR). Simulated values of the temperature coefficient for both design cases are smaller than 37ppm/°C.