Patent ID: 7812668

Claim:
A multi-input operational amplifier, comprising: a first transconductor configured to generate a first current in accordance with a voltage of a first input end and a first reference voltage, wherein the first current is a non-zero first constant if the voltage of the first input end is smaller than a first voltage, and the first current is proportional to the voltage of the first input end if the voltage of the first input end is between the first voltage and a second voltage; a second transconductor configured to generate a second current in accordance with a voltage of a second input end and a second reference voltage, wherein the second current is a non-zero second constant if the voltage of the second input end is smaller than a third voltage, and the second current is proportional to the voltage of the second input end if the voltage of the second input end is between the third voltage and a fourth voltage; a first current minor configured to generate a first mirror current in accordance with the first current; a second current minor configured to generate a second minor current in accordance with the second current; and a current source connected to the first current mirror and the second current mirror.