An amplifying circuit of a display device including a plurality of pixels includes an input unit, a bias unit, and an output unit. The input unit is coupled between a first power source for supplying a first voltage and a second power source for supplying a second voltage, receives a first input signal and a second input signal, and is controlled by the first and second input signals. The bias unit receives a bias voltage for operating the input unit, and includes a first node and a second node controllable by the input unit. The output unit applies an output voltage to a pixel by using a first output transistor turned on/off by a signal applied to the first node and a second output transistor turned on/off by a signal applied to the second node, and the first output transistor is a different type to the second output transistor. In this instance, the input unit includes a first input transistor having a first terminal coupled to a first power source and being turned on/off by a first input signal and a second input transistor of the same type as the first input transistor, having a first terminal coupled to the first power source, and being turned on/off by a second input signal. The bias unit includes a first transistor controllable by the on/off state of the first input transistor and a second transistor controllable by the on/off state of the second input transistor.