PURPOSE: A small number of transistors and a POR(Power On Reset) circuit are provided to control a voltage level of a detection node by using small number of transistors and resistance devices. CONSTITUTION: A current mirror(120) is connected to a power node to which variable power voltage is applied. The current mirror supplies currents through first and second lines. A comparing voltage generating unit(140) generates a comparing voltage through a current of a first line. A driving unit(200) is connected to a second line and activates a reset signal. A ground select transistor(GST) is connected to the second line.
