Patent ID: 7253687

Claim:
An operational amplifier having output voltage limitation, comprising: an operational amplifier having a differential input and an output, the differential input comprising a differentially connected transistor pair; a voltage clamp comprising a differentially connected transistor pair, wherein one transistor of the voltage clamp transistor pair is coupled to the differential input transistor pair and the output, and the other transistor of the voltage clamp transistor pair is coupled to a clamp voltage reference, such that when a voltage on the output of the operational amplifier is substantially equal to the clamp voltage reference the voltage clamp controls the output voltage of the operational amplifier; and a current mirror supplying current to the differentially connected input transistor pair and the one transistor of the voltage clamp transistor pair, wherein when the one transistor of the voltage clamp differential transistor pair draws substantially the same current as drawn by the differential input transistor pair and the output of the operational amplifier is thereby controlled to be at substantially the clamp voltage reference.