Patent ID: 7339430

Claim:
A rail-to-rail operational amplifier, comprising: a high-side differential input pair, controlled by a first input voltage and a second input voltage, for dividing a high-side bias current into two partial currents; a low-side differential input pair, controlled by the first input voltage and the second input voltage, for dividing a low-side bias current into two other partial currents; and a summing output stage for combining the two partial currents and the two other partial currents, and generating an output voltage on a basis of the combination, characterized by further comprising: a high-side current adjusting circuit for adjusting the high-side bias current on a basis of a comparison between the first and the second input voltages, for increasing the high-side bias current when an absolute value of a difference between the first and the second voltages increases under a condition that the first input voltage is smaller than the second input voltage, and a low-side current adjusting circuit for adjusting the low-side bias current on a basis of the comparison between the first and the second input voltages, for increasing the low-side bias current when the absolute value of the difference between the first and the second voltages increases under a condition that the first input voltage is larger than the second input voltage.