A detector circuit includes a first inverter including an input node coupled via a first capacitor to a transmission path for transmitting an AC signal, the first inverter outputting an output voltage in accordance with power of the AC signal, wherein the output voltage increases with increasing temperature, a second inverter including an input node coupled to the transmission path, the second inverter outputting an output voltage in accordance with power of the AC signal, wherein the output voltage decreases with increasing temperature, a third capacitor including one electrode coupled to either an output electrode of the first inverter or an output node of the second inverter, a first resistor coupled between the output node of the first inverter and an output node of the detector circuit, and a second resistor coupled between the output node of the second inverter and the output node of the detector circuit.