The invention relates to a trigger. The trigger comprises a high-level threshold comparator, a low-level threshold comparator, an or-not circuit with an enabling control function, and a phase inverter, wherein the output end of the high-level threshold comparator is electrically connected with the first input end of the or-not circuit with the enabling control function, the output end of the low-level threshold comparator is electrically connected with the second input end of the or-not circuit with the enabling control function, the output end of the or-not circuit with the enabling control function is electrically connected with the input end of the phase inverter, the output end of the phase inverter is fed back to the third input end of the or-not circuit with the enabling control function, and thus the trigger voltage of the front edge of the trigger and the trigger voltage of the rear edge of the trigger can be prevented from being influenced by supply voltage and temperature.