We demonstrate the key module of comparators in GaN ICs,based on resistor-transistor logic(RTL)on E-mode wafers in this work.The fundamental inverters in the comparator consist of a p-GaN gate HEMT and a 2DEG resistor as the load.The function of the RTL comparators is finally verified by a undervoltage lockout(UVLO)circuit.The compatibility of this cir-cuit with the current p-GaN technology paves the way for integrating logic ICs together with the power devices.