Patent ID: 7764121

Claim:
A differential amplifier comprising: an input circuit configured to generate first differential currents and second differential currents in response to a voltage difference between differential input signals; an output circuit including a first transistor connected between a first voltage rail and an output port and a second transistor connected between the output port and a second voltage rail; a current summing circuit including a first control node configured to output a first control voltage to control a current flowing in the first transistor in response to the first differential currents and a second control node configured to output a second control voltage to control a current flowing in the second transistor in response to the second differential currents; and a switch circuit connecting a gate of the first transistor to one of the first control node and the first voltage rail and a gate of the second transistor to one of the second control node and the second voltage rail, in response to a control signal, wherein the switch circuit comprises: a first switch configured to control a connection between the first control node and the gate of the first transistor in response to the control signal; a second switch configured to control a connection between the second control node and the gate of the second transistor in response to the control signal; a third switch configured to control a connection between the first voltage rail and the gate of the first transistor in response to the control signal; and a fourth switch configured to control a connection between the second voltage rail and the gate of the second transistor in response to the control signal.