An input buffer which detects an input signal. The input buffer including an output node, a first buffer, and a second buffer. The first buffer may control the voltage level of the output node when the voltage level of a reference voltage signal is equal to a predetermined voltage level. The second buffer may control the voltage level of the output node in response to the input signal when the voltage level of the reference voltage signal is lower than the predetermined voltage level. The second buffer may maintain the output node at a first level. The second buffer may include an output control section and a level control unit. The output control section may receive the input signal and generate a level output signal at a second level. The level control section may generate a control signal which maintains the output node at the first level, in response to the level output signal when the voltage level of the reference voltage signal is lower than the predetermined voltage level of the first voltage and may intercept the control signal when the voltage level of the reference voltage signal is equal to the predetermined voltage level.