Comparator circuit for comparing three inputs

An apparatus comprising:

• a differential amplifying unit configured to amplify a difference between a voltage at a first node and a voltage at a second node, and to output a resultant voltage;
• a first bias switch configured to control a current flowing to a ground voltage source from a first node to which a first current is supplied based on a first voltage;
• a second bias switch configured to control a part of a current flowing to said ground voltage source from said second node to which a second current is supplied based on a second voltage;
• a third bias switch configured to control a remaining part of a current flowing from said second node to said ground voltage source based on a third voltage;
• and
• a bias converting unit configured to supply a third bias current to said second node based on said second voltage and said third voltage.

An method comprising:

• forming a differential amplifying unit to amplify a difference between a voltage at a first node and a voltage at a second node, and output a resultant voltage;
• forming a current source to supply a first bias current to said first node and supply a second bias current to said second node;
• forming a first bias switch to bias a current flowing from said first node to a ground voltage source based on a first voltage;
• forming a second bias switch to bias a part of a current flowing from said second node to said ground voltage source based on a second voltage;
• forming a third bias switch to bias a remaining part of said current flowing from said second node to said ground voltage source based on a third voltage;
• and
• forming a bias converting unit to supply a third bias current to said second node based on said second voltage and said third voltage.