Auto-zero technique for opamps with a source-follower output stage based on replica referencing
AssigneeMicron Technology, Inc.
InventorMichele Piccardi
Life of this patent
Estimating the term…
Abstract
An electronic circuit comprises an input stage, a gain stage operatively coupled to the input stage, a primary output stage operatively coupled to the gain stage, a replica output stage operatively coupled to the gain stage in parallel to the primary output stage, and a clock circuit. The clock circuit operates the electronic circuit in multiple phases including a sampling phase to disconnect the primary output stage and the replica output stage from the gain stage to obtain an offset voltage, an active phase to reconnect the primary output stage to apply the offset voltage to reduce an offset at the primary output stage, and an intermediate phase to first reconnect the replica output stage to the gain stage prior to the active phase.
Claims19
An electronic circuit comprising:
- an input stage;
- a gain stage operatively coupled to the input stage;
- a primary output stage operatively coupled to the gain stage wherein the primary output stage is a source-follower output stage;
- a replica output stage operatively coupled to the gain stage in parallel to the primary output stage, wherein the replica output stage is a replica source-follower stage;
- and
- a clock circuit configured to operate the electronic circuit in multiple phases including:
- a sampling phase to disconnect the primary output stage and the replica output stage from the gain stage to obtain an offset voltage;
- an active phase to reconnect the primary output stage to apply the offset voltage to reduce an offset at the primary output stage;
- and
- an intermediate phase to first reconnect the replica output stage to the gain stage prior to the active phase.
A method of operating an operational amplifier (opamp) circuit, the method comprising:
- disconnecting a source-follower output stage of the opamp circuit and a replica source-follower stage of the opamp circuit from a gain stage of the opamp circuit;
- applying voltage of a first sample-and-hold capacitor to the source-follower output stage, and sampling an offset voltage of the gain stage and an input stage of the opamp circuit onto a second sample-and-hold capacitor;
- connecting a source or drain of an output transistor of the replica output stage to the gain stage;
- disconnecting the source or drain of the output transistor of the replica output stage from the gain stage;
- and
- reconnecting a gate of an output transistor of the source-follower output stage and applying the offset voltage to the gate of the output transistor of the source-follower output stage.
An electronic system comprising
- an operational amplifier (opamp) circuit including:
- an input stage;
- a gain stage;
- and
- a source-follower output stage;
- and
- an auto-zeroing circuit including;
- a replica source-follower stage operatively coupled to the gain stage in parallel the source follower output stage;
- and
- a clock circuit configured to operate the auto-zeroing circuit in multiple phases including:
- a sampling phase to disconnect the source-follower output stage and the replica source-follower stage from the gain stage to obtain an offset voltage;
- an active phase to reconnect the source-follower output stage to apply the offset voltage to reduce an offset at, the source-follower output stage;
- and
- an intermediate phase to first reconnect the replica source-follower stage to the gain stage prior to the active phase.
Dependencies are inferred from the claim text.