Abstract: With the analog to digital converter of three inverters, theoretical analysis and injection experiment of microwave effects are carried out on circuit unit level. The core chip of the circuit is 74HC04 or 74LVCU04A inverter. The latch process of the inverter is used to explain the nonlinear disturbance. The study is concentrated on the microwave effects on the circuit operating. Under the variation parameters of injected microwave pulse, such as amplitude, carrier frequency, and pulse width. At a fixed temperature, the threshold of effective injected microwave power for nonlinear disturbance of 10 % is 33 dBm for 74HC04 and 30 dBm for 74LVCU04A, when the carrier frequency of the injected microwave is below 3 GHz. The threshold increases with the increase of the carrier frequency. Additiona