Bandgap voltage reference circuit
A bandgap voltage reference circuit comprising: a first P-N junction circuit generating a first voltage which changes according to a first characteristic; a second P-N junction circuit generating a second voltage which changes according to a second characteristic different from the first characteristic; an amplifier receiving the first and second voltages at a pair of input terminals and changing the amount of an output current provided from a high-voltage power supply to an output terminal according to a difference voltage between the first and second voltages, wherein an output voltage at the output terminal is provided to the first and second P-N junction circuits; and an output current controller causing the amplifier to provide the output current to the output terminal regardless of the difference voltage when the output voltage equals to or is smaller than a threshold voltage.
1. A bandgap voltage reference circuit comprising:
a first circuit generating a first voltage which changes according to a first characteristic;
a second circuit generating a second voltage which changes according to a second characteristic different from the first characteristic;
an amplifier receiving the first and second voltages, and changing and supplying an amount of an output current from a first power supply to an output terminal according to a difference voltage between the first and second voltages, wherein an output voltage at the output terminal is provided to the first and second circuits; and
an output current controller providing a control signal to the amplifier to cause the amplifier to supply the output current from the first power supply to the output terminal regardless of the difference voltage when the output voltage equals or is smaller than a threshold voltage, wherein the output current controller connects with the output terminal and the amplifier.
2. The bandgap voltage reference circuit according to claim 1 , wherein:
the first circuit comprises first and second resistances and a first P-N junction element which are provided between the output terminal and a second power supply and generates the first voltage at a first coupling point between the first and second resistances; and
the second circuit comprises a third resistance and a second P-N junction element which are provided between the output terminal and the second power supply and generates the second voltage at a second coupling point between the third resistance and the second P-N junction element, wherein the second P-N junction element has a junction area smaller than that of the first P-N junction element.
3. The bandgap voltage reference circuit according to claim 1 , wherein the amplifier comprises:
a differential circuit generating a differential output signal dependent on the difference voltage; and
an output current supply circuit changing the amount of the output current according to the differential output signal.
4. The bandgap voltage reference circuit according to claim 3 , wherein the output current controller causes the amplifier to change the amount of the output current according to the difference voltage when the output voltage is greater than the threshold voltage.
5. The bandgap voltage reference circuit according to claim 3 , wherein:
the output current supply circuit comprises a current source provided between the first power supply and the output terminal and a pull-down device provided between the output terminal and the second power supply, the pull-down device having a conduction resistance which changes according to the differential output signal; and
the output current controller disables the pull-down device when the output voltage equals or is smaller than the threshold voltage.
6. The bandgap voltage reference circuit according to claim 3 , wherein:
the output current supply circuit comprises an output transistor provided between the first power supply and the output terminal for providing the output current to the output terminal;
the differential circuit drives the output transistor by using the differential output signal; and
the output current controller controls the differential output signal to increase the driving capability of the output transistor regardless of the difference voltage when the output voltage equals or is smaller than the threshold voltage.
7. The bandgap voltage reference circuit according to claim 6 , wherein:
the differential circuit comprises a current source coupled to the first power supply and a pull-down transistor coupled to the second power supply and generates the differential output signal at a coupling node between the current source and the pull-down transistor; and
the output current controller comprises an output current control transistor provided between the pull-down transistor and the second power supply or between the pull-down transistor and the coupling node and having a gate coupled to the output terminal.
8. The bandgap voltage reference circuit according to claim 3 , wherein:
the output current supply circuit comprises an output transistor provided between the first power supply and the output terminal and a pull-down transistor provided between the second power supply and a gate of the output transistor, the gate of the output transistor being driven by the differential output signal; and
the output current controller controls the pull-down transistor to control the differential output signal to increase a current output from the output transistor when the output voltage equals or is smaller than the threshold voltage.
9. The bandgap voltage reference circuit according to claim 1 , wherein:
the amplifier comprises an amplification section generating a differential output signal dependent on the difference voltage and a buffer circuit changing the amount of the output current according to the differential output signal;
the buffer circuit comprises a current source provided between the first power supply and the output terminal and a pull-down transistor provided between the output terminal and the second power supply, the pull-down transistor being controlled by the differential output signal; and
the output current controller comprises an output current control transistor provided between the pull-down transistor and the second power supply or between the pull-down transistor and a current source and having a gate coupled to the output terminal.
10. The bandgap voltage reference circuit according to claim 1 , wherein:
the amplifier comprises an amplification section generating a differential output signal dependent on the difference voltage and a buffer circuit changing the amount of the output current according to the differential output signal;
the buffer circuit comprises a current source coupled to the first power supply, a pull-down transistor provided between the current source and a second power supply and controlled by the differential output signal, and an output transistor provided between the current source and an output terminal, the output transistor having a gate coupled to a coupling node between the current source and the pull-down transistor and providing the output current to an output terminal; and
the output current controller comprises an output current control transistor provided between the pull-down transistor and the second power supply or between the pull-down transistor and the current source, the output current control transistor having a gate coupled to the output terminal.
11. The bandgap voltage reference circuit according to claim 2 , wherein the P-N junction element is a PNP bipolar transistor having a base and a collector which are coupled to the second power supply.
12. The bandgap voltage reference circuit according to claim 2 , wherein the P-N junction element is an NPN bipolar transistor having an emitter coupled to the second power supply and a base and a collector coupled with each other.
13. The bandgap voltage reference circuit according to claim 1 , wherein:
the operational amplifier becomes stable when the output voltage is at a first stable point and at a second stable point higher than the first stable point; and
the threshold voltage is higher than an output voltage at the first stable point.
14. A bandgap voltage reference circuit comprising:
a first circuit generating a first voltage which changes according to a first characteristic;
a second circuit generating a second voltage which changes according to a second characteristic different from the first characteristic;
an amplifier receiving the first and second voltages, and changing and supplying an amount of an output current from a power supply to an output terminal, according to a difference voltage between the first and second voltages, when an output voltage at the output terminal is greater than a threshold voltage, wherein the output voltage is provided to the first and second circuits; and
an output current controller being in an off gate when the output voltage equals or is smaller than the threshold voltage, and, when in the off state, causing a transistor within the amplifier to increase the output current and to supply the increased output current from the power supply to the output terminal regardless of the difference voltage, wherein the output current controller connects with the output terminal and the amplifier.