Operational amplifier input offset correction with transistor threshold voltage adjustment

A device, comprising:

• an operational amplifier (op amp) circuit having a transistor pair of the same conductivity type, a first transistor of the pair being formed in a first well and operational in a sensing of a voltage at a positive (+) input of the op amp, and a second transistor of the pair being formed in second well and operational in a sensing of a voltage applied at a negative (−) input of the op amp;
• a body bias generator configured to vary a first body bias voltage applied to the first well, and not the second well, that varies in response to a first body bias control value;
• and
• a control circuit configured to selectively generate the first body bias control value in response to an input offset voltage of the op amp.

A method, comprising:

• determining an offset voltage of an operational amplifier (op amp) having a positive (+) input and a negative (−) input;
• if the offset voltage is greater than a limit, making a change to at least a body bias voltage of a first transistor but not making the same change to a body bias voltage of a second transistor;
• determining the offset voltage of the op amp after the change to the body bias voltage;
• if the offset voltage is within the limit, using the body bias voltage as an operating body bias voltage for the op amp, and if the offset voltage remains greater than the limit, making another change to the body bias voltage of the first or second transistor;
• wherein
• the first transistor is coupled to one input of the op amp and the second transistor is coupled to the other input of the op amp.