Voltage reference circuit
AssigneeMotorola, Inc.
InventorRobert S. Wrathall
Life of this patent
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Abstract
A voltage reference source is provided which is temperature stable and can be made by standard CMOS processes. The voltage reference can provide an output voltage which is equal to twice the bandgap voltage. The voltage reference circuit uses a differential amplifier which has an output coupled to an additional amplifying stage. Two substrate bipolar transistors are used wherein the emitter current density of one of the transistors is larger than the emitter current density of the other transistor. An additional transistor is inserted between the output of the amplifying stage and the substrate bipolar transistors thereby providing the output voltage of twice the bandgap voltage.
Claims6
A voltage reference circuit having a differential amplifier with a first and a second input and an output, the voltage reference circuit comprising:
- a first transistor having a base coupled to the output of the differential amplifier and having a first electrode coupled to a first power terminal and having a second electrode;
- a second transistor having a base coupled to the second electrode of the first transistor, the second transistor also having a first electrode coupled to the first power terminal and having a second electrode;
- a first resistor coupled between the second electrode of the second transistor and a second power terminal;
- a third transistor having a base coupled to the second electrode of the second transistor and having a first electrode coupled to the first power terminal and having a second electrode;
- a second and a third resistor coupled in series between the second electrode of the third transistor and the second power terminal and forming a node between the second and third resistor, the node being coupled to the first input of the differential amplifier;
- a fourth transistor having a base coupled to the base of the third transistor and having a first electrode coupled to the first power terminal and having a second electrode;
- and a fourth resistor coupled between the second electrode of the fourth transistor and the second power terminal, and the second electrode of the fourth transistor also being coupled to the second input of the differential amplifier.
Dependencies are inferred from the claim text.