Dynamic input stage biasing for low quiescent current amplifiers

An amplifier having dynamic input stage biasing, the amplifier comprising:

• a controlled current source being responsive to a control signal for at least partially controlling an input bias current generated by the controlled current source;
• an input stage comprising a differential pair including first and second active devices, each active device being operatively coupled to first and second inputs, respectively, of the amplifier, the active devices being operatively coupled to the controlled current source at a tail node;
• and an input load operatively coupled to the differential pair;
• and
• a sense circuit operatively connected in a feedback arrangement between an output of the amplifier and the controlled current source, the sense circuit measuring an output load current from the amplifier and generating the control signal in response thereto;
• whereby the input bias current is a function of the output load current of the amplifier.

An amplifier having dynamic input stage biasing, the amplifier comprising:

• an input stage operatively coupled to an input of the amplifier;
• a controlled current source operatively coupled to the input stage, the controlled current source being responsive to a control signal for at least partially controlling an input bias current generated by the controlled current source;
• a sense circuit operatively connected in a feedback arrangement between an output of the amplifier and the controlled current source, the sense circuit measuring an output load current from the amplifier and generating the control signal in response thereto;
• and
• a second stage including a first input coupled to the input stage of the amplifier, a second input for receiving a second control signal, and an output coupled to the output of the amplifier, the second stage being responsive to the second control signal for controlling a current flowing through the second stage;
• whereby the current flowing through the second stage and the input bias current are functions of the output load current of the amplifier.

An amplifier having dynamic input stage biasing, the amplifier comprising:

• an input stage operatively coupled to an input of the amplifier;
• a controlled current source operatively coupled to the input stage, the controlled current source being responsive to a control signal for at least partially controlling an input bias current generated by the controlled current source, wherein the controlled current source comprises first and second NMOS transistors, each transistor having a gate terminal, a source terminal and a drain terminal, the drain terminal of the first transistor being connected to the input stage, the source terminal of the first transistor being connected to the drain terminal of the second transistor and to the control signal, the source terminal of the second transistor being connected to a current return of the amplifier, the gate terminals of the first and second transistors being coupled to first and second bias voltages, respectively;
• and
• a sense circuit operatively connected in a feedback arrangement between an output of the amplifier and the controlled current source, the sense circuit measuring an output load current from the amplifier and generating the control signal in response thereto;
• whereby the input bias current is a function of the output load current of the amplifier.

A regulator circuit including an unregulated input and a regulated output and having dynamic input stage biasing, the regulator comprising:

• an error amplifier including first and second inputs and an output, the error amplifier including an input stage operatively coupled to the first and second inputs of the error amplifier, and a controlled current source operatively coupled to the input stage, the controlled current source being responsive to a control signal for at least partially controlling an input bias current generated by the controlled current source, the error amplifier generating an error signal in response to a difference between a reference voltage coupled to the first input of the error amplifier and a measured voltage representing at least a portion of the regulated output of the regulator;
• a pass device having a first terminal coupled to the unregulated input of the regulator, a second terminal coupled to the regulated output of the regulator, and a third terminal coupled to the output of the error amplifier, the pass device receiving the error signal and controlling a voltage drop between the first and second terminals of the pass device in response thereto;
• a sense circuit operatively connected in a feedback configuration between the output of the regulator and the controlled current source in the error amplifier, the sense circuit measuring an output load current from the regulator and generating the control signal in response thereto;
• whereby the input bias current of the error amplifier is a function of the output load current of the regulator.

A method of reducing quiescent current of an amplifier, the method comprising the steps of:

• sensing a signal presented to an output device associated with the amplifier, the output device supplying an output current from the amplifier, at least when the amplifier is loaded, which varies in response to the signal presented to the output device;
• generating a control signal that is representative of at least a portion of the signal presented to the output device;
• and
• controlling an input bias current flowing through an input stage of the amplifier in response to the control signal;
• whereby the input bias current is dynamically controlled as a function of the signal presented to the output device.

An integrated circuit including an amplifier comprising:

• an input stage operatively coupled to an input of the amplifier;
• a controlled current source operatively coupled to the input stage, the controlled current source being responsive to a control signal for at least partially controlling an input bias current generated by the controlled current source;
• an output device operatively coupled to an output of the amplifier, the output device supplying an output load current, at least when the amplifier is loaded, which varies in response to an input signal presented to the output device;
• and
• a sense circuit operatively connected in a feedback arrangement between the output device and the controlled current source, the sense circuit measuring at least a portion of the input signal presented to the output device and generating the control signal that is representative thereof;
• whereby the input bias current is dynamically controlled as a function of the input signal presented to the output device.

An integrated circuit including an amplifier comprising:

• a controlled current source being responsive to a control signal for at least partially controlling an input bias current generated by the controlled current source;
• an input stage comprising a differential pair including first and second active devices, each active device being operatively coupled to first and second inputs, respectively, of the amplifier, the active devices being operatively coupled to the controlled current source at a tail node;
• and an input load operatively coupled to the differential pair;
• and
• a sense circuit operatively connected in a feedback arrangement between an output of the amplifier and the controlled current source, the sense circuit measuring an output load current from the amplifier and generating the control signal in response thereto;
• wherein the input load includes an input for receiving a second control signal for controlling a current flowing through the input load in response thereto, whereby the current flowing through the input load and the input bias current are functions of the output load current of the amplifier.

An integrated circuit including an amplifier comprising:

• an input stage operatively coupled to an input of the amplifier;
• a controlled current source operatively coupled to the input stage, the controlled current source being responsive to a control signal for at least partially controlling an input bias current generated by the controlled current source;
• a sense circuit operatively connected in a feedback arrangement between an output of the amplifier and the controlled current source, the sense circuit measuring an output load current from the amplifier and generating the control signal in response thereto;
• and
• a second stage including a first input coupled to the input stage of the amplifier, a second input for receiving a second control signal, and an output coupled to the output of the amplifier, the second stage being responsive to the second control signal for controlling a current flowing through the second stage;
• whereby the input bias current and the current flowing through the second stage are functions of the output load current of the amplifier.

An integrated circuit including an unregulated input and a regulated output, the integrated circuit comprising:

• an error amplifier including first and second inputs and an output, the error amplifier comprising an input stage operatively coupled to the first and second inputs of the error amplifier, and a controlled current source operatively coupled to the input stage, the controlled current source being responsive to a control signal for at least partially controlling an input bias current generated by the controlled current source, the error amplifier generating an error signal in response to a difference between a reference voltage coupled to the first input of the error amplifier and a measured voltage representing at least a portion of the regulated output of the integrated circuit;
• a pass device having a first terminal coupled to the unregulated input of the integrated circuit, a second terminal coupled to the regulated output of the integrated circuit, and a third terminal coupled to the output of the error amplifier, the pass device receiving the error signal and controlling a voltage drop between the first and second terminals of the pass device in response thereto;
• a sense circuit operatively connected in a feedback configuration between the regulated output of the integrated circuit and the controlled current source in the error amplifier, the sense circuit measuring an output load current from the integrated circuit and generating the control signal in response thereto;
• whereby the input bias current of the error amplifier is a function of the output load current of the integrated circuit.