Devices and methods for offset cancellation

An offset-cancellation circuit comprising:

• an input amplifier comprising a first input, a second input, a first output, and a second output;
• a pre-storage amplifier comprising a first input and a second input;
• a post-storage amplifier comprising a first input coupled with a first plate of a first storage capacitor and comprising a second input coupled with a first plate of a second storage capacitor;
• wherein in a first state of the offset-cancellation circuit:
• the first input of the input amplifier and the second input of the input amplifier are coupled to a common mode to produce a voltage offset between the first output of the input amplifier and the second output of the input amplifier;
• the first input of the pre-storage amplifier is coupled to the first output of the input amplifier and the second input of the pre-storage amplifier is coupled to the second output of the input amplifier;
• the first plate of the first storage capacitor is coupled with a first output of the pre-storage amplifier and the first plate of the second storage capacitor is coupled with a second output of the pre-storage amplifier;
• and
• wherein a first potential is stored on the first storage capacitor and a second potential is stored on the second storage capacitor, a difference between the first potential and the second potential being proportional to the voltage offset;
• and
• wherein in a second state of the offset-cancellation circuit:
• the first input of the pre-storage amplifier is de-coupled to the first output of the input amplifier and the second input of the pre-storage amplifier is de-coupled to the second output of the input amplifier;
• the first plate of the first storage capacitor is decoupled from the first output of the pre-storage amplifier;
• the first plate of the second storage capacitor is decoupled from the second output of the pre-storage amplifier;
• and
• a first output of the post-storage amplifier is coupled with the first output of the input amplifier and a second output of the post-storage amplifier is coupled with the second output of the input amplifier to provide a first offset-cancellation current to the first output of the input amplifier and a second offset-cancellation current to the second output of the input amplifier, the first offset-cancellation current and the second offset-cancellation current determined by the first potential and by the second potential.

A method to cancel an offset voltage of an amplifier comprising:

• generating the offset voltage between a first output of the amplifier and a second output of the amplifier by coupling a first input of the amplifier and a second input of the amplifier to a common mode;
• receiving the offset voltage at a first input of a first amplification stage and a second input of the first amplification stage;
• storing a potential difference determined by a first gain of the first amplification stage and the offset voltage in a storage element configured to be coupled and decoupled with a first output of the first amplification stage and a second output of the first amplification stage;
• decoupling the first input of the first amplification stage from the first output of the amplifier and decoupling the second input of the first amplification stage from the second output of the amplifier;
• decoupling the storage element from first amplification stage and providing the potential difference between a first input of a second amplification stage and a second input of the second amplification stage, the second amplification stage comprising a second gain;
• and
• providing an offset-cancellation current to the first output of the amplifier and the second output of the amplifier from a first output of the second amplification stage and a second output of the second amplification stage, the offset-cancellation current determined by the second gain and the potential difference and wherein the offset-cancellation current comprises a first current at the first output of the second amplification stage and a second current at the second output of the second amplification stage.