An inverter includes a first PMOS transistor having a gate electrode coupled to a first input port, a first electrode coupled to a first node and a second electrode coupled to the gate electrode or a second power source; a second PMOS transistor having a gate electrode coupled to the first input port, and first and second electrodes coupled respectively to a first power source and an output port; a third PMOS transistor having a gate electrode coupled to the first node, first and second electrodes coupled respectively to the output port and a second input port; and a capacitor coupled between the first node and the output port.