Abstract: A high-speed and high-precision constant current output drive circuit is designed in this paper. The current precision of the driver circuit is improved by eliminating the mismatch of the feedback loop and increasing the output impedance. The turn-on speed of output current is enhanced by reducing the overdrive voltage of the power transistor. The proposed driver circuit was fabricated in a 0.18 μm BCD process. It occupies only 0.1 mm² chip area. The chip tested result show that the current accuracy is ±0.16% when the output current is 60 mA for the output voltage range from 0.3V to 4.5V. While the current accuracy is ±0.12% when the output current is 120 mA for the output voltage range from 0.55V to 4.5 V. The turn-on time is only 20 ns for an output current of 120mA.