Calibrating the DC-offset of amplifiers

An amplifier circuit, comprising:

• an amplifier including:
• an input to receive an input signal,
• an output to provide an output signal, and
• a plurality of primary devices coupled between the input and the output;
• at least one secondary device, the at least one secondary device being substantially smaller than each of the plurality of primary devices;
• and
• at least one switch coupled to at least one of the amplifier and the at least one secondary device to selectively couple the at least one secondary device to the amplifier to alter the effective size of at least one of the plurality of primary devices to compensate for an offset voltage of the amplifier.

An amplifier circuit, comprising:

• an amplifier element arranged to be configured as an amplifier during a period of normal operation and to be configured as a comparator during a calibration period, the amplifier element including at least one device coupled to an internal node of the amplifier element, the at least one device having an operating parameter control lead to control an operating parameter of the at least one device;
• a logic circuit coupled to an output of the amplifier element at least during the calibration period to receive an output signal from the output of the amplifier element and to output an offset compensation control signal;
• and
• an offset compensation control circuit coupled to the logic circuit and to the operating parameter control lead of the at least one device to receive the offset compensation control signal from the logic circuit and provide a parameter control signal to the operating parameter control lead to control a particular operating parameter of the at least one device to compensate for an offset voltage of the amplifier element.

An amplifier circuit, comprising:

• an amplifier connected to be configured as a comparator during a calibration period, the amplifier including:
• an input to receive an input signal,
• an output to provide an output signal, and
• at least one transistor included in a current mirror of the amplifier, the at least one transistor being coupled to an internal node of the amplifier and having an operating parameter control lead to control an operating parameter of the at least one transistor;
• a logic circuit coupled to the output of the amplifier at least during the calibration period to receive a signal from the output of the amplifier and to output an offset compensation control signal;
• and
• an offset compensation control circuit coupled to the logic circuit and to the operating parameter control lead of the at least one transistor to receive the offset compensation control signal from the logic circuit and provide a parameter control signal to the operating parameter control lead to control a particular operating parameter of the at least one transistor to compensate for an offset voltage of the amplifier.

An amplifier circuit, comprising:

• an amplifier element arranged to be configured as an amplifier during a period of normal operation and to be configured as a comparator during a calibration period;
• a logic circuit coupled to an output of the amplifier element at least during the calibration period to receive an output signal from the output of the amplifier element and to output an offset compensation control signal, the logic circuit being configured to, responsive to a clock signal, increase the offset compensation control signal if the signal from the output of the amplifier element is in a first logic state and decrease the offset compensation control signal if the signal from the output of the amplifier element is in a second logic state;
• and
• an offset compensation control circuit coupled to the logic circuit and the amplifier element to receive the offset compensation control signal from the logic circuit and, responsive to the offset compensation control signal, to compensate for an offset voltage of the amplifier element.

A method for controlling an offset voltage of an amplifier element, comprising the steps of:

• configuring the amplifier element as a comparator during a calibration period;
• coupling a controllable voltage source that generates only an offset compensation voltage for the amplifier element between a pair of inputs of the amplifier element;
• responsive to an output of the amplifier element, generating an offset compensation control signal that controls the offset compensation voltage;
• responsive to the offset compensation control signal, adjusting the offset compensation voltage until the offset compensation voltage approximates an inherent offset voltage of the amplifier element;
• and
• configuring the amplifier element as an amplifier during a period of normal operation.

A method for controlling an offset voltage of an amplifier element, comprising the steps of:

• configuring the amplifier element as a comparator during a calibration period;
• connecting a pair of inputs of the amplifier element to one of a common node and two nodes having known voltages thereon;
• responsive to an output signal of the amplifier element, selectively adjusting a level of an operating parameter of at least one device included in or coupled to the amplifier element to compensate for the offset voltage of the amplifier element;
• and
• configuring the amplifier element as an amplifier during a period of normal operation.

A method for compensating for an offset voltage of an amplifier element including the septs of:

• configuring the amplifier element as a comparator during a calibration period;
• connecting a pair of inputs of the amplifier element to one of a common node and two nodes having known voltages thereon;
• and
• responsive to a first logic state at an output of the amplifier element, increasing a value of the compensation signal that controls the offset compensation of the amplifier element;
• responsive to a second logic state at the output of the amplifier element, decreasing the value of the compensation signal that controls the offset compensation of the amplifier element;
• and
• configuring the amplifier element as an amplifier during a period of normal operation.