Low drift voltage reference
First Claim
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1. A voltage reference circuit comprising:
- a zener diode, including an anode, a cathode, and a positive temperature coefficient for a voltage generated between the anode and the cathode; and
a temperature compensation circuit, connected to the cathode of the zener diode, configured to provide a temperature stable output voltage reference by subtracting from the voltage at the cathode of the zener diode, a series of base-emitter voltage differences respectively provided by bipolar transistors having different emitter current densities, wherein the temperature compensation circuit includes a series of base-emitter voltage difference circuits to generate the series of base-emitter voltage differences, wherein a base emitter voltage difference circuit is arranged in a cell, the cell comprising;
a plurality of bipolar transistors arranged in first, second and third arms of the cell and configured to generate a proportional to absolute temperature voltage at an output of the cell that is dependent on individual ones of the plurality of bipolar transistors, and wherein each of the first arm, second arm and third arms are coupled to a single bias current such that the bias current is divided into each of the arms and each of the arms compensates for base current variations in the other of the arms.
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Abstract
Circuits and method for providing voltage reference circuits that include low drift over time and lower operating voltages are provided. Generally, it is desirable that a reference circuit provide an accurate and precise reference over time. The voltage reference circuits described can provide for good long term stability, operation at lower voltages than prior designs, consistent output voltage with reduced variability due to process changes and mismatches, low noise in the reference voltage, and other advantages.
33 Citations
20 Claims
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1. A voltage reference circuit comprising:
a zener diode, including an anode, a cathode, and a positive temperature coefficient for a voltage generated between the anode and the cathode; and
a temperature compensation circuit, connected to the cathode of the zener diode, configured to provide a temperature stable output voltage reference by subtracting from the voltage at the cathode of the zener diode, a series of base-emitter voltage differences respectively provided by bipolar transistors having different emitter current densities, wherein the temperature compensation circuit includes a series of base-emitter voltage difference circuits to generate the series of base-emitter voltage differences, wherein a base emitter voltage difference circuit is arranged in a cell, the cell comprising;
a plurality of bipolar transistors arranged in first, second and third arms of the cell and configured to generate a proportional to absolute temperature voltage at an output of the cell that is dependent on individual ones of the plurality of bipolar transistors, and wherein each of the first arm, second arm and third arms are coupled to a single bias current such that the bias current is divided into each of the arms and each of the arms compensates for base current variations in the other of the arms.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A voltage reference circuit comprising:
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a first set of circuit elements comprising a zener diode having a positive temperature coefficient for a voltage generated between an anode and a cathode of the zener diode; a second set of circuit elements comprising a series of base-emitter voltage difference circuits that include ratiometrically scaled pairs of bipolar transistors configured to generate a-proportional to absolute temperate (PTAT) voltage, wherein a ratiometrically scaled pair of bipolar transistors includes a first bipolar transistor having a first emitter area and a second bipolar transistor having a second different emitter area scaled to the first emitter area; and the circuit coupling each of the first and second set of circuit elements to subtract the PTAT voltage from a voltage at the cathode of the zener diode to generate a temperature stable voltage reference at an output of the circuit, wherein the second set of circuit elements are arranged in a cell, the cell comprising;
a plurality of bipolar transistors arranged in first, second and third arms of the cell and configured to generate a proportional to absolute temperature voltage at an output of the cell that is dependent on individual ones of the plurality of bipolar transistors, and wherein each of the first arm, second arm and third arms are coupled to a single bias current such that the bias current is divided into each of the arms and each of the arms compensates for base current variations in the other of the arms. - View Dependent Claims (18)
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19. A method of providing a voltage reference comprising:
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generating a series of base-emitter voltage differences respectively provided by bipolar transistors having different emitter current densities; and coupling a zener diode to the bipolar transistors, the bipolar transistors being configured to generate a negative base-emitter voltage differential having a complimentary to absolute temperature, CTAT, voltage form which compensates for a proportional to absolute temperature, PTAT, temperature coefficient of the zener diode to provide at an output of the circuit a voltage reference having a first order temperature insensitivity, wherein the generating the series of base-emitter voltage differences includes arranging a plurality of bipolar transistors in first, second and third arms of a cell and generating a proportional to absolute temperature voltage at an output of the cell that is dependent on individual ones of the plurality of bipolar transistors, and dividing a single bias current into each of the first, second and third arms of the cell such that each of the arms compensates for base current variations in the other of the arms of the cell.
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20. A voltage reference circuit comprising a zener diode coupled to circuit elements configured to generate a negative base-emitter voltage differential, Δ
- Vbe, component, the negative Δ
Vbe component compensating for positive temperature coefficient response characteristics of the zener diode to provide a voltage reference at an output of the voltage reference circuit,wherein; the circuit elements are arranged in a cell, the cell comprising; a plurality of bipolar transistors arranged in first, second and third arms of the cell and configured to generate a proportional to absolute temperature voltage at an output of the cell that is dependent on individual ones of the plurality of bipolar transistors, and each of the first arm, second arm and third arms are coupled to a single bias current such that the bias current is divided into each of the arms and each of the arms compensates for base current variations in the other of the arms, the circuit elements comprise; a first PNP transistor having a unity emitter size; a second PNP transistor having a multiple, n, emitter size; a third PNP transistor having a unity emitter size; and a PMOS transistor, the first PNP transistor has its emitter connected to a positive supply node, its base connected to the base of the second PNP transistor and the emitter of the third PNP transistor, and its collector connected to the base of the third PNP transistor and a current source, the second PNP transistor has its emitter connected to an output node and the drain of the PMOS transistor, and its collector connected to a second current source and the gate of the PMOS transistor, the third PNP transistor has its collector coupled to ground, and the PMOS transistor has its source connected to the positive supply node.
- Vbe, component, the negative Δ
Specification