Bandgap voltage reference circuit
AssigneeNational Semiconductor Corporation
InventorA. Karl Rapp
Life of this patent
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Abstract
A bandgap voltage reference circuit includes a feedback controlled current mirror, a bandgap voltage generator, and a voltage comparator. The current mirror, in response to a feedback control signal from the voltage comparator, generates a controllable reference current. The bandgap voltage generator generates two reference voltages based upon conduction of the reference current from the current mirror through two PN diodes having different emitter areas. The voltage comparator compares the two reference voltages and generates the feedback control signal for the current mirror. Such a bandgap voltage reference circuit simultaneously generates a bandgap voltage reference and a current mirror reference while also being operable over a wide power supply voltage range and down to very low power supply voltage values.
Claims18
An apparatus including a bandgap voltage generator comprising:
- a current source configured to receive a control signal and in accordance therewith provide an input current which is adjustable in accordance with said control signal, wherein said current source includes a current shunt configured to be coupled across a current conductor and receive said control signal, and wherein said current conductor conducts a series current, said current shunt conducts a shunt current in accordance with said control signal and said input current comprises a sum of said series current and said shunt current;
- a current amplifier, coupled to said current source, configured to conduct said input current and in accordance therewith conduct an output current which is proportional to said input current;
- a voltage generator, coupled to said current amplifier, including first and second PN junction devices having first and second current densities, and configured to receive said output current and in accordance therewith generate first and second voltages, wherein said first and second voltages are approximately proportional to said output current and are dependent upon said first and second current densities, respectively;
- and
- a voltage comparator, coupled to said voltage generator and said current source, configured to receive and compare said first and second voltages and in accordance therewith provide said control signal such that said first and second voltages are equal.
An apparatus including a bandgap voltage generator comprising:
- a reference voltage generator including a controllable shunt circuit configured to receive a control signal, generate a shunt current which is adjustable in accordance with said control signal and generate a reference voltage which is adjustable in accordance with said shunt current;
- a voltage converter, coupled to said reference voltage generator, including first and second PN junction devices having first and second current densities, and configured to receive said reference voltage and generate first and second voltages which are dependent upon said first and second current densities, respectively, and are adjustable in accordance with said reference voltage;
- and
- a voltage comparator, coupled to said voltage converter and said reference voltage generator, configured to receive and compare said first and second voltages and in accordance therewith provide said control signal such that said first and second voltages are equal.
A method of generating a bandgap voltage, said method comprising the steps of:
- receiving a control signal and in accordance therewith generating an input current which is adjustable in accordance with said control signal by
- conducting a series current with a current conductor, and
- coupling across said current conductor and receiving a control signal and in accordance therewith conducting a shunt current, wherein said input current comprises a sum of said series current and said shunt current;
- conducting said input current and in accordance therewith conducting an output current which is proportional to said input current;
- receiving said output current with first and second PN junction devices having first and second current densities and in accordance therewith generating first and second voltages which are approximately proportional to said output current and are dependent upon said first and second current densities, respectively;
- and
- receiving and comparing said first and second voltages and in accordance therewith generating said control signal such that said first and second voltages are equal.
A method of generating a bandgap voltage, said method comprising the steps of:
- receiving a control signal with a controllable shunt circuit and generating therewith a shunt current which is adjustable in accordance with said control signal;
- generating a reference voltage which is adjustable in accordance with said shunt current;
- receiving said reference voltage with a circuit which includes first and second PN junction devices having first and second current densities and in accordance therewith generating first and second voltages which are dependent upon said first and second current densities, respectively, and are adjustable in accordance with said reference voltage;
- and
- receiving and comparing said first and second voltages and in accordance therewith generating said control signal such that said first and second voltages are equal.
Dependencies are inferred from the claim text.