Differential amplifier and filter circuit using the same

A differential amplifier comprising:

• a first current source one end of which is connected to a power supply or a ground;
• a first MOS transistor of a first conductivity type whose drain is connected to the other end of said first current source and whose gate is connected to a first input terminal;
• a second MOS transistor of the first conductivity type whose source is connected to a source of said first MOS transistor and whose gate is connected to a second input terminal;
• a third MOS transistor of the first conductivity type whose drain is connected to the sources of said first and second MOS transistors, whose source is connected to the ground or the power supply, and whose gate is coupled to the other end of said first current source;
• a second current source one end of which is connected to the power supply or the ground;
• a fourth MOS transistor of the first conductivity type whose drain is connected to the other end of said second current source and whose gate is connected to said second input terminal;
• a fifth MOS transistor of the first conductivity type whose source is connected to a source of said fourth MOS transistor and whose gate is connected to said first input terminal;
• and
• a sixth MOS transistor of the first conductivity type whose drain is connected to the sources of said fourth and fifth MOS transistors, whose source is connected to the ground or the power supply, and whose gate is coupled to the other end of said second current source, wherein
• a differential signal is inputted to said first and second input terminals and a differential output is obtained from drains of said second and fifth MOS transistors.