Fast transient response enhancement circuit for LDO

In this paper, a fast transient enhancement circuit for LDO is proposed. This structure improves the problem of overshoot and undershoot voltage and long stability time when the traditional LDO loads are transient. The push-pull amplifier structure is introduced to double the charging and discharging current of the power transistor when the transient state changes. In addition, the two currents of the push-pull amplifier can be duplicated by making use of the replicable characteristics of the two branches of the amplifier, and the subtraction operations of in-phase and inverse phase are performed respectively, so as to control the opening and closing of the two transient enhancement circuits. Since the transient enhancement current is copied by the current mirror, the magnitude of the transient enhancement current can be controlled to a certain extent. Under the typical load switching state, the proposed scheme can control the overshoot voltage within 35mV and the undershoot voltage within 24mV. Compared with the traditional LDO structure, the overshoot voltage and undershoot voltage are increased by 84% and 77% respectively, and the recovery time of overshoot and undershoot is increased by 30% and 32% respectively.