Comparator

A comparator comprising:

• a main body comparator of a differential amplifier type including:
• a pair of input MOSFETs in a differential pair receiving a reference voltage and an input voltage at a respective gate of the input MOSFETs;
• and
• a pair of load MOSFETs having gates thereof connected to each other and drains thereof connected to respective drain of the input MOSFETs;
• and
• a constant current source to supply a constant current to sources of the input MOSFETs;
• and
• Zener diodes exhibiting a breakdown voltage lower than a withstand voltage of a gate oxide film of the input MOSFETs and connected between a gate and a source of each of the input MOSFETs in parallel in a forward direction;
• and
• a feedback MOSFET that performs negative feedback of an output voltage of the main body comparator to gates of the load MOSFETs to restrict an amplitude of an output voltage of the main body comparator.

A comparator comprising:

• a main body comparator of a differential amplifier type including:
• a pair of input MOSFETs in a differential pair receiving a reference voltage and an input voltage at a respective gate of the input MOSFETs;
• and
• a pair of load MOSFETs having gates thereof connected to each other and drains thereof connected to respective drain of the input MOSFETs;
• and
• a constant current source to supply a constant current to sources of the input MOSFETs;
• and
• Zener diodes exhibiting a breakdown voltage lower than a withstand voltage of a gate oxide film of the input MOSFETs and connected between a gate and a source of each of the input MOSFETs in parallel in a forward direction;
• and
• a feedback MOSFET that performs negative feedback of an output voltage of the main body comparator to gates of the load MOSFETs to restrict an amplitude of an output voltage of the main body comparator;
• and
• semiconductor rectifying elements that exhibit a reverse blocking characteristic higher than a power supply voltage and are interposed between the constant current source and a source of each input MOSFET.

An apparatus, comprising:

• a comparator configured to compare an input voltage to a reference voltage and output a resulting output voltage;
• a first logic device having a withstand voltage and coupled to an input terminal to be connected to the input voltage;
• a second logic device having a withstand voltage and coupled to a terminal of the reference voltage;
• a first circuit element having a breakdown voltage and connected to the input terminal and to a terminal of the first logic device;
• and
• a second circuit element having a breakdown voltage and connected to the terminal of the reference voltage and to a terminal of the second logic device;
• wherein the breakdown voltage of each of the first circuit element and the second circuit element is lower than the withstand voltage of each of the first logic device and the second logic device.