Patent ID: 7714645

Claim:
A single-ended operational amplifier having a first mode and a second mode, comprising: an output stage having a first input, a second input, and a first output; a first transconductance amplifier having a third input, a fourth input, a second output connected to the first input, and a third output connected to the second input; a second transconductance amplifier having a fifth input, a sixth input, a fourth output connected to the first input, and a fifth output connected to the second input; and a capacitor connected between the fifth input and the sixth input; wherein in the first mode, the third input and the fourth input are supplied with a reference voltage, and the first output is connected to the sixth input, so as for offset cancellation for the single-ended operational amplifier; and in the second mode, the third input and the fourth input are connected to two inputs of the single-ended operational amplifier respectively, and the first output is connected to an output of the single-ended operational amplifier.