A differential amplifier and a method for generating a computer simulation model thereof are disclosed. The device is thermally stable through adoption of a ballast resistor to a differential structure of a unit transistor pair, such that the differential amplifier prevents heat effect phenomena, such as performance deterioration and device destruction by heating, and, at the same time, improves or maintains other performances, thereby achieving high gain, high efficiency, high linearity, and wide bandwidth characteristics. Therefore, the differential amplifier can be easily designed as undesired effects of parasitic resistor of emitter or via or bonding wire, etc. for the differential amplifier are reduced in a differential mode.