Patent ID: 7471150

Claim:
A class AB folded cascode circuit comprising: (a) a differential current follower circuit including i. first and second cascode transistors each having a first electrode, a second electrode, and a control electrode, the control electrodes being coupled to a bias voltage source; the differential current follower circuit having a first input conductor coupled to the first electrode of the first cascode transistor, a second input conductor coupled to the first electrode of the second cascode transistor, a first output conductor coupled to the second electrode of the first cascode transistor, and a second output conductor coupled to the second electrode of the second cascode transistor; ii. a first current mirror circuit having an input coupled to the first input conductor and an output coupled to the second output conductor; and iii. a second current mirror circuit having an input coupled to the second input conductor and an output coupled to the first output conductor; the differential current follower circuit producing a differential output current at the first and second output conductors which follows a differential input current applied at the first and second input conductors; and (b) a third current mirror circuit for performing a conversion of differential output current in the first and second output conductors to a corresponding single-ended output voltage on the second output conductor; wherein the output of the first current mirror circuit is coupled to the second output conductor by means of a third cascode transistor having a first electrode coupled to the output of the first current mirror circuit, a second electrode coupled to the second output conductor, and a control electrode coupled to the bias voltage source; and wherein the output of the second current mirror circuit is coupled to the first output conductor by means of a fourth cascode transistor having a first electrode coupled to the output of the second current mirror circuit, a second electrode coupled to the first output conductor, and a control electrode coupled to the bias voltage source.