Amplifier circuit having high linearity for cancelling third order harmonic distortion

An amplifier having a first differential input, a second differential input, an input for receiving a bias voltage, a first differential output, and a second differential output, the amplifier comprising:

• a first transistor having a first electrode coupled to the first differential output of the amplifier, a control electrode coupled to the input of the amplifier, and a second electrode;
• a first resistor having a first terminal coupled to said second electrode of said first transistor and a second terminal coupled to the first differential input of the amplifier;
• a second resistor having a first terminal coupled to the first differential input of the amplifier and a second terminal;
• a second transistor having a first electrode and a control electrode coupled in common to said second terminal of said second resistor, and a second electrode coupled for receiving a power supply voltage;
• a third transistor having a first electrode coupled to the second differential output of the amplifier, a control electrode coupled to said control electrode of said second transistor, and a second electrode coupled for receiving said power supply voltage;
• a fourth transistor having a first electrode coupled to the second differential output of the amplifier, a control electrode coupled to the input of the amplifier, and a second electrode;
• a third resistor having a first terminal coupled to said second electrode of said fourth transistor and a second terminal coupled to the second differential input of the amplifier;
• a fourth resistor having a first terminal coupled to the second differential input of the amplifier and a second terminal;
• a fifth transistor having a first electrode and a control electrode coupled in common to said second terminal of said fourth resistor, and a second electrode coupled for receiving said power supply voltage;
• and
• a sixth transistor having a first electrode coupled to the first differential output of the amplifier, a control electrode coupled to said control electrode of said fifth transistor, and a second electrode coupled for receiving said power supply voltage.

An amplifier comprising:

• a first transistor having a first electrode, a control electrode coupled for receiving a bias voltage, and a second electrode;
• a first resistor having a first terminal coupled to said second electrode of said first transistor and a second terminal coupled to a first input of the amplifier;
• a second transistor having a first electrode and a control electrode coupled in common to said first input of the amplifier, and a second electrode;
• and
• a second resistor having a first terminal coupled to said second electrode of said second transistor and a second terminal coupled for receiving a power supply voltage wherein said first transistor provides a signal at said first electrode that has a linear relationship to an input signal applied to said first input of the amplifier wherein said first and second resistors have an impedance approximately one half an impedance of said first and second transistors for nulling out a third harmonic distortion.