A regulator circuit according to one embodiment includes a first transistor, a filter, and a differential amplifier. The first transistor is provided between an input terminal on a power supply side and an output terminal on an output side. The differential amplifier includes an output node connected to the first transistor, and controls the first transistor on the basis of a result of comparison between a reference voltage and a feedback voltage according to an output voltage applied to the output terminal. The filter is connected to a control node that makes a differential pair with the output node, in the differential amplifier.

Methods related to controlling switches. In some embodiments, a method for controlling a radio-frequency switch can include providing or generating a control signal to allow generation of a plurality of reference levels by a regulator, or to allow the regulator to be in sleep mode. The method can further include operating the regulator based on the control signal to generate the plurality of reference voltage levels for operation of the radio-frequency switch, or to be in the sleep mode.

Methods related to controlling switches. In some embodiments, a method for controlling a radio-frequency switch can include providing or generating a control signal to allow generation of a plurality of reference levels by a regulator, or to allow the regulator to be in sleep mode. The method can further include operating the regulator based on the control signal to generate the plurality of reference voltage levels for operation of the radio-frequency switch, or to be in the sleep mode.

A voltage regulator includes an output transistor, an error amplifier coupled to the output transistor, a cascode transistor coupled to the output transistor in series, and a cascode bias circuit coupled to the cascode transistor and the output transistor. The output transistor is configured to generate an output signal at a first voltage. The error amplifier is configured to receive a reference signal. The cascode bias circuit is configured to bias the cascode transistor such that, in response to a drain-to-source short circuit of the output transistor, the cascode transistor generates the output signal at the first voltage.

A voltage regulator includes an output transistor, an error amplifier coupled to the output transistor, a cascode transistor coupled to the output transistor in series, and a cascode bias circuit coupled to the cascode transistor and the output transistor. The output transistor is configured to generate an output signal at a first voltage. The error amplifier is configured to receive a reference signal. The cascode bias circuit is configured to bias the cascode transistor such that, in response to a drain-to-source short circuit of the output transistor, the cascode transistor generates the output signal at the first voltage.

A low dropout regulator is disclosed. The low dropout regulator includes an amplifier, a first transistor, a second transistor and a switch. When a supply voltage value of the low dropout regulator is less than a supply voltage threshold value, a first path of the switch is selected and a first switch voltage value is transmitted to the first transistor so as to fully conduct the first transistor, and an output voltage value of the low dropout regulator is equal to the supply voltage value. When the supply voltage value is not less than the supply voltage threshold value, a second path of the switch is selected and a second switch voltage value is transmitted to the first transistor so as to turn off the first transistor, and the output voltage value is adjusted by the second transistor and the amplifier.

Low leakage current switch controller. In some embodiments, a controller for a radio-frequency switch can include a low-dropout regulator configured to generate a plurality of reference voltage levels for operation of a switch, or to be in a sleep mode to conserve power, based on a control signal received through a common input node. The controller can further include a mode detector in communication with the low-dropout regulator, and be configured to provide a first form of the control signal to the common input node to allow the plurality of reference levels to be generated by the low-dropout regulator, or a second form of the control signal to the common input node to put the low-dropout regulator in the sleep mode.

Low leakage current switch controller. In some embodiments, a controller for a radio-frequency switch can include a low-dropout regulator configured to generate a plurality of reference voltage levels for operation of a switch, or to be in a sleep mode to conserve power, based on a control signal received through a common input node. The controller can further include a mode detector in communication with the low-dropout regulator, and be configured to provide a first form of the control signal to the common input node to allow the plurality of reference levels to be generated by the low-dropout regulator, or a second form of the control signal to the common input node to put the low-dropout regulator in the sleep mode.

Circuits, systems, and methods to automatically switch modes to provide constant reference voltages are discussed herein. For example, a bandgap reference system may include a first bandgap reference circuit configured to provide a first bandgap reference voltage, a low dropout regulator coupled to the first bandgap reference circuit, a temperature circuit coupled to the low dropout regulator, and a second bandgap reference circuit coupled to the low dropout regulator and the temperature circuit. The second bandgap reference circuit may be configured to configure one or more impedance elements based at least in part on a temperature signal and provide a second bandgap reference voltage based on one or more currents that pass through the one or more impedance elements.

Circuits, systems, and methods to automatically switch modes to provide constant reference voltages are discussed herein. For example, a bandgap reference system may include a first bandgap reference circuit configured to provide a first bandgap reference voltage, a low dropout regulator coupled to the first bandgap reference circuit, a temperature circuit coupled to the low dropout regulator, and a second bandgap reference circuit coupled to the low dropout regulator and the temperature circuit. The second bandgap reference circuit may be configured to configure one or more impedance elements based at least in part on a temperature signal and provide a second bandgap reference voltage based on one or more currents that pass through the one or more impedance elements.