Differential amplifier and calculation amplifier

A differential amplifier comprising:

• first and second input terminals to which a differential signal composed of first and second signals is inputted;
• first and second level shift circuits for shifting respective voltages of the first and second signals inputted to the first and second input terminals;
• a first differential couple and a first current source for converting the differential signal level-shifted by the first and second level shift circuits to currents;
• a second differential couple and a second current source for converting the differential signal inputted to the first and second input terminals to currents;
• a third current source and a reference voltage source;
• a comparator for comparing the voltage of the first or second signal inputted to the first or second input terminal with a voltage of the reference voltage source;
• a switch circuit for selectively supplying a current from the third current source to the first or second current source depending on a result of the comparison by the comparator;
• and
• first and second output terminals to which an output of the first differential couple and an output of the second differential couple are connected commonly.