Folded cascode amplifier having improved slew performance
AssigneeLinear Technology Corporation
InventorHengsheng Liu
Life of this patent
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Abstract
A folded cascode amplifier having improved slew comprises an input differential transistor pair circuit, a cascode branch circuit coupled to the differential pair circuit, and a boost circuit for increasing branch current when the amplifier is in a slew condition. The additional current increases slew of the amplifier without negatively affecting amplifier characteristics.
Claims14
A folded-cascode amplifier circuit, comprising:
- a differential input circuit including a differential transistor pair coupled to a source of tail current and to a differential input signal for responsively conducting a differential first current;
- a cascode branch coupled to the differential input circuit for supplying a second current thereto;
- and
- a boost circuit for increasing the second current only when the amplifier is slewing at least at a prescribed rate of slew, and the boost circuit including a transconductance amplifier responsive to the differential first current for increasing the second current.
A method of improving slew performance of a folded-cascode amplifier of a type having an input differential circuit for dividing a tail current selectively between sides of the input differential circuit in response to an input differential signal, a cascode branch circuit coupled to the input differential circuit for supplying a branch current to the input differential circuit, and a boost circuit including a transconductance amplifier responsive to the differential first current for increasing the branch current, comprising the steps of determining amplifier slew, and increasing the branch current only when the amplifier is slewing at a prescribed rate of slew.
Dependencies are inferred from the claim text.