Low dropout regulator and circuit system using same

The invention provides a low dropout regulator for limiting quiescent current, which comprises an error amplifier, an output switch transistor, a feedback switch transistor, a current copying circuit and a clamping current source, and is characterized in that the clamping current source is additionally arranged between an input voltage and the feedback switch transistor; the feedback current output by the feedback switch transistor is clamped, and the maximum feedback current is only proportional to the current value of the clamping current source. Therefore, the quiescent current output by the low dropout regulator is no longer in direct proportion to the load current and is increased without limitation, and the technical problems of poor stability, efficiency reduction and the like caused by infinite increase of the quiescent current can be effectively solved. 本发明提供了一种限制静态电流的低压降稳压器，低压降稳压器包括误差放大器、输出开关晶体管、回授开关晶体管、电流复制电路和钳制电流源，通过在输入电压与回授开关晶体管之间增设钳制电流源，使得回授开关晶体管所输出的回授电流受到钳制，最高仅正比于钳制电流源的电流值。如此一来可令低压降稳压器所输出的静态电流不