Patent ID: 7605654
Filing Date: 2009-10-20
Classification: H03F

Abstract:
1. A telescopic operational amplifier (OPAMP), comprising: a current source; an input stage, coupled to the current source and comprising a group of input transistors, for receiving an input voltage, wherein the group of input transistors comprises a first input transistor and a second input transistor connected to the first input transistor, and the first and second input transistors are coupled between the current source and the load stage; and a load stage, coupled to the input stage and comprising a group of load transistors, for outputting an output voltage, wherein the threshold voltages of the group of input transistors are larger than that of the group of the load transistors, wherein the group of load transistors comprises: a plurality of first load transistors connected to the first input transistor in series between a voltage source and the current source, wherein a gate of one of the first load transistors is coupled to a gate of the first input transistor for receiving the input voltage; and a plurality of second load transistors connected to the second input transistor in series between the voltage source and the current source, wherein a gate of one of the second load transistors is coupled to a gate of the second input transistor for coupling the output voltage.