In the power semiconductor market， insulated gate bipolar transistor （IGBT） and silicon carbide metal-oxide-semiconductor field-effect transistors （SiC MOSFETs） have excellent voltage resistance and frequency characteristics， and thus gradually replaced the traditional MOSFETs. The reliability design of IGBT and SiC MOSFET driver circuits is associated with rigorous challenges. Therefore， an optocoupler-isolated gate driver chip was designed in this study. Monolithic integration was realized by co-designing photodetectors and driver circuits. Silveraco software was used to simulate the photodetector. The simulation results indicate that the responsivity of the photodetector to 800 nm infrared light is 0.277 A/W， and the -3 dB bandwidth is approximately 90 MHz. Further， the optical structure of the optocoupler was optimized to effectively isolate the control end and the rear high-voltage drive circuit， and thus the crosstalk problem was addressed. The 0.18 μm 40 V bipolar-CMOS-DMOS （BCD） technique was used to tape out and test the package chip. The chip test results indicate that the chip propagation delay is only 98 ns when the input current of the light source is 10 mA， the chip power supply voltage is 12–40 V， and the input signal frequency is 20 kHz.