Operational amplifier having a wide input/output range and an improved slew rate

An operational amplifier including:

• an input stage having a first differential transistor pair composed of a pair of transistors connected between a first constant current source and two output nodes and having control electrodes connected to two signal input terminals, respectively, so that a signal applied between said two signal input terminals is amplified in a differential manner, and an output signal is obtained from a selected output node of said two output nodes;
• an output stage having two output transistors of different conductivity types, connected in series between two power supply terminals, a connection node between said two output transistors being connected to an output signal terminal, and a level shift circuit receiving said output signal of said input stage for generating a level-shifted signal of said output signal of said input stage;
• said output signal of said input stage and said level-shifted signal being applied to control electrodes of said two output transistors, respectively, so that said two output transistors drive said output signal terminal in a push-pull manner;
• and
• a capacitance between said selected output node of said input stage and said output signal terminal,
• said input stage including a first bias current supplementing means connected in parallel to said first constant current source, for selectively supplying an additional bias current to said first differential transistor pair in accordance with said level-shifted signal.