Embodiments may disclose a power on reset circuit, which includes: a current mirror connected to a power node, the power node receiving a variable power supply voltage, the current mirror being configured to supply a first current to a first line and a second current to a second line; a comparative voltage generator configured to generate a comparative voltage using the first current provided via the first line; a driver connected to the second line, the driver being configured to activate a reset signal in response to a voltage of the second line; and a ground selecting transistor configured to connect the second line and a ground node according to the comparative voltage.