High speed low power op-amp circuit

An operational amplifier circuit comprising:

• an input stage configured to receive a differential input signal and providing a differential output, said input stage comprising:
• cascaded first and second emitter follower transistors and cascaded third and fourth emitter follower transistors, said input stage having a first input terminal connected to a base of said first emitter follower transistor, and having a second input terminal connected to a base of said third emitter follower transistor, wherein said first emitter follower transistor has an emitter coupled to a base of said second emitter follower transistor and said third emitter follower transistor has an emitter coupled to a base of said fourth emitter follower transistor;
• and
• cascaded fifth and sixth emitter follower transistors and cascaded seventh and eighth emitter follower transistors for developing a complementary differential output, wherein a base of said fifth emitter follower transistor is coupled to said first input terminal and wherein a base of said seventh emitter follower transistor is coupled to said second input terminal, said fifth emitter follower transistor having an emitter coupled to a base of said sixth emitter follower transistor, said seventh emitter follower transistor having an emitter coupled to a base of said eighth emitter follower transistor;
• a current mirror stage connected to a collector of said second emitter follower transistor and to a collector of said fourth emitter follower transistor so as to be coupled to receive said differential output of said input stage, and configured to a single-ended output;
• a complementary current mirror stage connected to a collector of said sixth emitter follower transistor and to a collector of said eighth emitter follower transistor so as to be coupled to receive said complementary differential output, and configured to produce a single-ended output;
• and
• means for commonly coupling said outputs of said current mirror and said complementary current mirror together to produce said single-ended output, wherein an emitter output terminal of said second emitter follower transistor is connected to an emitter output terminal of said sixth emitter follower transistor to form a first node, wherein an emitter output terminal of said fourth emitter follower transistor is connected to an emitter output terminal of said eighth emitter follower transistor to form a second node, said operational amplifier further comprising an impedance element coupled between said first node and said second node, said impedance element developing a current indicative of a potential difference applied between said first input terminal and said second input terminal of said circuit.