A waveform generator capable of generating a square wave and a ramp wave using one switching element is provided. A waveform generator includes a first transistor having a drain electrode, a gate electrode, and a source electrode. A first resistor and a first diode are coupled at a common node between a first input terminal and the gate electrode. A second resistor is coupled between the gate electrode and a second input terminal. A first capacitor is coupled between the drain electrode and the common node between the first resistor and the first diode.