A zero-pole compensation technique used in low noise LDO

In order to improve the stability of Low-Drop Out Linear Regulator (LDO) and reduce the noise generated by the feed-forward circuit, a low-noise feed-forward circuit that generates an adaptive compensation zero point is proposed. The feed-forward circuit forms a high-gain feedback signal through the low-value feedback resistor through the load current of the mirror pass transistor, and couples with the LDO output voltage to the signal transmitted to the feedback end through the feedback network to form a controllable zero point controlled by the load capacitance and load current, which can effectively improve the overall stability of the LDO circuit. In addition, an adaptive current compensation circuit that generates dynamic poles is added to ensure that the secondary poles do not affect the phase margin of the loop. Based on the 0.18 μm BCD process, the phase margin of the circuit is higher than 48° under a wide load range of 0 mA to 800 mA and a 5 V input 3.3 V output, and the applicable load capacitance range is ≥ 1 μF. At the same time, the output noise of the LDO is only 5.0617 μVrms in the frequency range of 10 kHz to 100 kHz.