Patent ID: 7323934

Claim:
An operational transconductance amplifier (OTA) for receiving a differential input voltage and outputting an output current, wherein the differential input voltage comprises a first input voltage and a second input voltage; the OTA comprising: a first current source, a second current source and a third current source for providing a first source bias current, a second source bias current and a third source bias current, respectively, wherein the first source bias current and the third source bias current are the same; a first current sink, a second current sink and a third current sink for providing a first sink bias current, a second sink bias current and a third sink bias current, respectively, wherein the first sink bias current and the third sink bias current are the same; a first differential unit biased by the first source bias current and the first sink bias current for receiving the second input voltage; a second differential unit biased by the second source bias current and the second sink bias current for receiving the first input voltage; a third differential unit biased by the third source bias current and the third sink bias current for receiving the second input voltage, wherein the third differential unit is coupled to the first differential unit and the third differential unit has the substantially same configuration as the first differential unit; a voltage-to-current converting unit coupled between the first and the second differential units for providing a conversion current according to the voltage difference between the first input voltage and the second input voltage; and a current subtraction device for outputting the output current obtained from a subtraction between a first output current multiplied by a factor and a second output current multiplied by the factor, wherein the first output current is provided by the first differential unit according to the first source bias current, the first sink bias current and the conversion current, and the second output current is provided by the third differential unit according to the third source bias current and the third sink bias current.