Circuits and methods to produce a vptat and/or a bandgap voltage with low-glitch preconditioning

A method for generating a voltage proportional to absolute temperature (VPTAT), comprising:

• producing a first base-emitter voltage (VBE1) by providing a first amount of current to a first circuit branch;
• producing a second base-emitter voltage (VBE2) by providing a second amount of current to a second circuit branch, where the second amount of current is less than the first amount of current;
• producing the VPTAT based on the first base-emitter voltage (VBE1) and the second base-emitter voltage (VBE2);
• changing over time which transistors are in the first circuit branch and the second circuit branch;
• preconditioning a said transistor with a current substantially equal to the second amount of current, after the said transistor is switched out of the first circuit branch, but before the said transistor is switched into the second circuit branch;
• and
• preconditioning a said transistor with a current substantially equal to the first amount of current, after the said transistor is switched out of the second circuit branch, but before the said transistor is switched into the first circuit branch.

A bandgap voltage reference circuit, comprising:

• a group of X transistors, each of which includes a base and a current path between a collector and an emitter;
• a plurality of switches configured to selectively change how at least some of the X transistors are connected within the circuit;
• a first circuit portion that generates a voltage complimentary to absolute temperature (VCTAT) using at least one of the X transistors;
• and
• a second circuit portion that generates a voltage proportional to absolute temperature (VPTAT) that is added to the VCTAT to produce a bandgap voltage output (VGO), the second circuit portion comprising:
• a first base-emitter voltage branch configured to provide a first amount of current to the current path of each transistor within the first base-emitter voltage branch to produce a first base-emitter voltage (VBE1);
• and
• a second base-emitter voltage branch configured to provide a second amount of current to the current path of each transistor within the second base-emitter voltage branch to produce a second base-emitter voltage (VBE2), where the second amount of current is less than the first amount of current;
• wherein the VPTAT is produced based on the first base-emitter voltage (VBE1) and the second base-emitter voltage (VBE2);
• a first current preconditioning branch configured to provide a current substantially equal to the first amount of current to each transistor within the first current preconditioning branch;
• and
• a second current preconditioning branch configured to provide a current substantially equal to the second amount of current to each transistor within the second current preconditioning branch;
• wherein the switches are used to selectively change over time which of the X transistors are in the first base-emitter voltage branch, the second base-emitter voltage branch, the first current preconditioning branch, and the second current preconditioning branch.

A method for producing a bandgap voltage, comprising:

• producing a first base-emitter voltage (VBE1) by providing a first amount of current to a first circuit branch;
• producing a second base-emitter voltage (VBE2) by providing a second amount of current to a second circuit branch;
• producing a voltage complimentary to absolute temperature (VCTAT) using a CTAT branch;
• producing a voltage proportional to absolute temperature (VPTAT) based on the first base-emitter voltage (VBE1) and the second base-emitter voltage (VBE2);
• and
• producing the bandgap voltage based on the VCTAT and the VPTAT;
• changing over time which transistors are in the first circuit branch and the second circuit branch;
• preconditioning a said transistor with a current substantially equal to the second amount of current, after the said transistor is switched out of the first circuit branch, but before the said transistor is switched into the second circuit branch;
• and
• preconditioning a said transistor with a current substantially equal to the first amount of current, after the said transistor is switched out of the second circuit branch, but before the said transistor is switched into the first circuit branch.

A voltage regulator, comprising:

• a bandgap voltage reference circuit to produce a bandgap voltage output (VGO);
• and
• an operation amplifier including
• a non-inverting (+) input that receives the bandgap voltage output (VGO),
• an inverting (−) input, and
• an output that produces the voltage output (VOUT) of the voltage regulator;
• wherein the bandgap voltage reference circuit includes
• a group of X transistors, each of which includes a base and a current path between a collector and an emitter;
• a plurality of switches configured to selectively change how at least some of the X transistors are connected within the circuit;
• a first circuit portion that generates a voltage complimentary to absolute temperature (VCTAT) using at least one of the X transistors;
• and
• a second circuit portion that generates a voltage proportional to absolute temperature (VPTAT) that is added to the VCTAT to produce a bandgap voltage output (VGO), the second circuit portion comprising:
• a first base-emitter voltage branch configured to provide a first amount of current to the current path of each transistor within the first base-emitter voltage branch to produce a first base-emitter voltage (VBE1);
• and
• a second base-emitter voltage branch configured to provide a second amount of current to the current path of each transistor within the second base-emitter voltage branch to produce a second base-emitter voltage (VBE2), where the second amount of current is less than the first amount of current;
• wherein the VPTAT is produced based on the first base-emitter voltage (VBE1) and the second base-emitter voltage (VBE2);
• a first current preconditioning branch configured to provide a current substantially equal to the first amount of current to each transistor within the first current preconditioning branch;
• and
• a second current preconditioning branch configured to provide a current substantially equal to the second amount of current to each transistor within the second current preconditioning branch;
• wherein the switches are used to selectively change over time which of the X transistors are in the first base-emitter voltage branch, the second base-emitter voltage branch, the first current preconditioning branch, and the second current preconditioning branch.