Patent ID: 8598914

Claim:
A comparator circuit, comprising: first and second MOSFETs whose sources are commonly connected, and to whose gates are supplied first and second input voltages used for comparison; a tail resistor interposed between a common connection point of the sources of the first and second MOSFETs and a first power source; third and fourth MOSFETs whose sources are connected to a second power source whose voltage differs from that of the first power source, whose gates are connected to the drain of the first MOSFET, and whose drains are connected to the drains of the first and second MOSFETs; a fifth MOSFET whose gate is connected to the gate and drain of the third MOSFET; and a constant voltage device of which one end is connected to the drain of the fifth MOSFET, wherein a voltage between the voltage of the first power source and the voltage of the second power source, having a predetermined difference from the voltage of the first power source, is input into the gate of the first MOSFET as the first input voltage, a voltage of a connection point of the drains of the second and fourth MOSFETs is output as a signal showing a result of a comparison between the first and second input voltages, and the constant voltage device is a Zener diode.