The present invention discloses a bias current generation circuit. An operation amplifier compares an input voltage having a zero-temperature coefficient and a feedback voltage to generate a driving voltage. An output transistor generates a bias current according to the driving voltage. A variable resistive circuit is electrically coupled to the output transistor through a feedback node to generate the feedback voltage according to the bias current and includes series-coupled resistors and switch transistors. Each of the resistors has a resistance having a positive temperature coefficient and includes a current input terminal and a current output terminal. Each of the switch transistors is electrically coupled between the current output terminal of one of the resistors and a ground terminal. One of the switch transistors turns on according to a control voltage variable according to the temperature variation to enable resistors to generate the resistance having a negative temperature coefficient.

Examples are disclosed herein that relate to automatically limiting an output current of a voltage regulator circuit responsive to detecting that the voltage regulator is in a current overload mode. In one example, a voltage regulator circuit includes an amplifier stage and a current limiter stage electrically connected to an output of the amplifier stage. The amplifier stage is configured to output a DC voltage based on a reference voltage and feedback from an output voltage. The current limiter stage is configured to operate in a quiescent mode and an overload mode. In the quiescent mode, the current limiter stage is configured to operate as a buffer stage that forms a closed feedback loop to an input of the amplifier stage. In the overload mode, the current limiter stage is configured to act as a current source that clamps an output current to a designated current.

Examples are disclosed herein that relate to automatically limiting an output current of a voltage regulator circuit responsive to detecting that the voltage regulator is in a current overload mode. In one example, a voltage regulator circuit includes an amplifier stage and a current limiter stage electrically connected to an output of the amplifier stage. The amplifier stage is configured to output a DC voltage based on a reference voltage and feedback from an output voltage. The current limiter stage is configured to operate in a quiescent mode and an overload mode. In the quiescent mode, the current limiter stage is configured to operate as a buffer stage that forms a closed feedback loop to an input of the amplifier stage. In the overload mode, the current limiter stage is configured to act as a current source that clamps an output current to a designated current.

A constant voltage generator circuit is provided with an operational amplifier including a feedback circuit having a first resistor, and an output transistor. The operational amplifier generates a feedback voltage generated by dividing an output voltage between an output terminal and a substrate voltage potential of the constant voltage generator circuit by the first resistor and a second resistor. Then, the operational amplifier is configured to amplify a voltage potential difference between a predetermined reference voltage and the feedback voltage and to output a control voltage. The output transistor controls an output voltage based on the control voltage from the operational amplifier, and the feedback circuit is further configured to superimpose high-frequency noise components from the substrate voltage potential onto the feedback voltage.

A constant voltage generator circuit is provided with an operational amplifier including a feedback circuit having a first resistor, and an output transistor. The operational amplifier generates a feedback voltage generated by dividing an output voltage between an output terminal and a substrate voltage potential of the constant voltage generator circuit by the first resistor and a second resistor. Then, the operational amplifier is configured to amplify a voltage potential difference between a predetermined reference voltage and the feedback voltage and to output a control voltage. The output transistor controls an output voltage based on the control voltage from the operational amplifier, and the feedback circuit is further configured to superimpose high-frequency noise components from the substrate voltage potential onto the feedback voltage.

An example apparatus includes power amplification circuitry and current-level switch circuitry. The power amplification circuitry has a first input port, a second input port, and field-effect transistor (FET) circuitry, the FET circuitry to operate in a saturation mode while drawing power provided at the first input port from a first power source. The current-level switch circuitry is to sense a change in a current-level used to maintain the FET circuitry in the saturation mode and, in response to the sensed change in the current-level, to cause the power amplification circuitry to draw power provided at the second input port from a second power source while maintaining the saturation mode of the FET circuitry.

An example apparatus includes power amplification circuitry and current-level switch circuitry. The power amplification circuitry has a first input port, a second input port, and field-effect transistor (FET) circuitry, the FET circuitry to operate in a saturation mode while drawing power provided at the first input port from a first power source. The current-level switch circuitry is to sense a change in a current-level used to maintain the FET circuitry in the saturation mode and, in response to the sensed change in the current-level, to cause the power amplification circuitry to draw power provided at the second input port from a second power source while maintaining the saturation mode of the FET circuitry.

A device includes a current source, a first transistor connected between a first supply rail and an output terminal, and a second transistor connected between the output terminal and a first terminal of the current source, wherein a second terminal of the current source is connected to a second supply rail. A variable-gain amplifier circuit responds to a potential at the first terminal of the current source by applying a potential to the control terminal of the first transistor. A gain of the amplifier circuit is determined by a potential at the output terminal.

A device includes a current source, a first transistor connected between a first supply rail and an output terminal, and a second transistor connected between the output terminal and a first terminal of the current source, wherein a second terminal of the current source is connected to a second supply rail. A variable-gain amplifier circuit responds to a potential at the first terminal of the current source by applying a potential to the control terminal of the first transistor. A gain of the amplifier circuit is determined by a potential at the output terminal.

Examples are disclosed herein that relate to automatically limiting an output current of a voltage regulator circuit responsive to detecting that the voltage regulator is in a current overload mode. In one example, a voltage regulator circuit includes an amplifier stage and a current limiter stage electrically connected to an output of the amplifier stage. The amplifier stage is configured to output a DC voltage based on a reference voltage and feedback from an output voltage. The current limiter stage is configured to operate in a quiescent mode and an overload mode. In the quiescent mode, the current limiter stage is configured to operate as a buffer stage that forms a closed feedback loop to an input of the amplifier stage. In the overload mode, the current limiter stage is configured to act as a current source that clamps an output current to a designated current.