Low-voltage LDO Compensation Strategy based on Current Amplifiers

In this communication, we propose a Miller compensation technique for low voltage LDO regulators which makes use of a current amplifier. The analysis shows how to design the compensation network when no voltage buffer is placed between the LDO error amplifier and power device and suggests a low supply voltage circuit topology that allows to compensate with a reasonably low integrated capacitance, to avoid oscillations due to the complex-conjugate poles at high output currents and to obtain acceptable under/overshoots during fast transient load variations. The designed LDO regulator can work with a supply voltage down to 1.2 V with a drop-out voltage of 200 mV at maximum load current of 100 mA; the integrated compensation capacitance is 25 pF, the load capacitor being equal to 1 muF. Simulations in good agreement with the theoretical results are also shown.