Differential amplifier adapted to be integrated in C-MOS monolithic IC

A differential amplifier comprising:

• an input stage differential amplifier circuit for amplifying a differential input signal;
• an output stage differential amplifier circuit taking the differential output of said input stage differential amplifier as a differential input;
• first and second common-mode current generating transistors receiving differential outputs of said output stage differential amplifier circuit at respective controlling electrodes and generating common-mode currents corresponding to the received differential outputs;
• a current mirror circuit inputting a composite current of the common-mode current generated by said first and second common-mode current generating transistors;
• and
• composing means for feeding back a current corresponding to an output mirror current of said current mirror circuit to a constant current source of said input stage differential amplifier circuit and composing therewith,
• said composing means including reference current generating transistor having a controlling electrode applied with a constant bias, and a differential current of the reference current and said output mirror current being fed back to the constant current source of said input stage differential amplifier circuit for composition,
• wherein said input stage differential amplifier circuit comprises a first pair of differential transistors supplied with the differential input signal at controlling electrodes, a constant current transistor supplying an operation current for said first pair of differential transistors, and a pair of load transistors connected between an output electrode of said first pair of differential transistors and a first power source and serving as active loads for said first pair of differential transistors;
• and
• said output stage differential amplifier circuit comprises a second pair of differential transistors supplied with the differential outputs of said input stage differential amplifier circuit at controlling electrodes thereof and having a common electrode connected to said first power source, and a pair of load transistors connected between said second pair of differential transistors and a second power source and serving as active loads for said second pair of differential transistors.