A bandgap voltage reference core circuit includes: a generating circuit, a first voltage dividing circuit and a second voltage dividing circuit. The generating circuit is configured to generate a positive temperature coefficient voltage and a negative temperature coefficient voltage, and obtain a positive temperature coefficient current and a negative temperature coefficient current based on the positive temperature coefficient voltage and the negative temperature coefficient voltage. The first voltage dividing circuit is connected to the generating circuit and the second voltage dividing circuit respectively, and is configured to generate an initial current based on the positive temperature coefficient current and the negative temperature coefficient current. The second voltage dividing circuit is configured to determine a reference voltage based on the initial current. The first voltage dividing circuit and the second voltage dividing circuit affect a voltage dividing proportion of the reference voltage.

Circuits, systems, and methods to switch modes based on temperature and to provide reference voltages are discussed herein. For example, a bandgap reference circuit may include one or more impedance elements and one or more switches coupled to the one or more impedance elements. The one or more switches may be controllable based on a temperature signal. The bandgap reference circuit may be configured to provide a bandgap reference voltage that is associated with less than a particular amount of voltage variation.

Multiple temperature-proportional cores are implemented within a bandgap circuit to deliver respective, uncorrelated temperature-proportional currents to a temperature-complementary load, reducing flicker noise in the resulting bandgap reference voltage.

A ratiometric current source circuit having a reduced temperature dependence is disclosed. An embodiment of the current source circuit includes a first divider circuit configured to generate a reference voltage using a voltage level of a power supply node and a second divider circuit including a first resistor with a first temperature coefficient and a second resistor with a second temperature coefficient. The first resistor is configured to generate a first current using an input voltage and the voltage level of the power supply node and the second resistor is configured to generate a second current using the input voltage. The embodiment further includes a buffer circuit configured to generate the input voltage using the reference voltage and generate an output current using a difference between the first current and the second current.

A voltage generation circuit may include: a first transistor coupled to an internal supply voltage terminal, and configured as a diode-connected transistor; a second transistor coupled to the first transistor and configured as a diode-connected transistor; and a third transistor coupled between the second transistor and a ground voltage terminal, and configured to operate according to a first reference voltage generated based on an external supply voltage. The voltage generation circuit may limit a variation in level of a second reference voltage which is generated through a drain terminal of the second transistor as a threshold voltage of the second transistor rises according to a rise in level of the internal supply voltage.

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.

Trimming components within an oscillator comprising: a trim-capable current source, wherein the trim-capable current source comprises a trimmable resistor and a trimmable current component, a comparator comprising a first input terminal that couples to the trim-capable current source and the second input terminal that couples to a reference voltage source, a switch coupled to the first input terminal and the trim-capable current source, and a trim-capable capacitor coupled to the switch, wherein the switch is coupled between the trim-capable capacitor and the trim-capable current source.

A temperature dependent correction circuit includes a first supply source, a second supply source, a rectifying circuit, and a reference. The first supply source is configured to supply a first signal that varies with temperature along a first constant or continuously variable slope. The second supply source is configured to supply a second signal that varies with temperature along a second constant or continuously variable slope. The rectifying circuit is configured to receive the first and second signal, rectify the first signal to produce a first rectified signal, and add the first rectified signal to the second signal to produce a correction signal. The reference is configured to receive the correction signal.

Trimming components within an oscillator comprising: a trim-capable current source, wherein the trim-capable current source comprises a trimmable resistor and a trimmable current component, a comparator comprising a first input terminal that couples to the trim-capable current source and the second input terminal that couples to a reference voltage source, a switch coupled to the first input terminal and the trim-capable current source, and a trim-capable capacitor coupled to the switch, wherein the switch is coupled between the trim-capable capacitor and the trim-capable current source.

A front-end module comprises a low-dropout (LDO) voltage regulator, a reference current generator, and a power amplifier. The LDO voltage regulator, reference current generator, and power amplifier are integrated on a first semiconductor die.