Low voltage high-output-driving CMOS voltage reference with temperature compensation
First Claim
1. A temperature-compensated reference-voltage generator comprising:
- a first stage that generates a complementary-to-absolute-temperature current that increases as temperature decreases;
a second stage that generates a proportional-to-absolute-temperature current that increases as temperature increases;
a summing resistor that receives both the complementary-to-absolute-temperature current from the first stage and the proportional-to-absolute-temperature current from the second stage, the summing resistor generating a summing voltage that is less dependent on temperature than either the complementary-to-absolute-temperature current or the proportional-to-absolute-temperature current;
a final voltage divider, in the second stage, that generates a reference voltage that includes the summing voltage;
an output transistor, coupled to the final voltage divider, for driving current to an output node, the output node being a node between the output transistor and the final voltage divider, the output node being driven by the output transistor to maintain the reference voltage on the output node; and
a final op amp having an output that drives a gate of the output transistor, the final op amp having a first input connected to a first sensing node in the second stage, and a second input connected to a second sensing node in the second stage;
wherein the first stage further comprises;
a first reference transistor that generates a first reference voltage that is complementary-to-absolute-temperature;
a first voltage divider coupled to the first reference voltage and generating a first compare voltage;
a first op amp that receives the first compare voltage and generates a bias voltage; and
a ctat current mirror transistor that receives the bias voltage from the first op amp, and generates the complementary-to-absolute-temperature current applied to the summing resistor, wherein the ctat current minor transistor is connected to the summing resistor;
a first current minor transistor that receives the bias voltage from the first op amp and generates a first current;
wherein the first current minor transistor is coupled to the first reference transistor and to the first voltage divider;
a second current minor transistor that receives the bias voltage from the first op amp and generates a second current;
a compare resistor that receives the second current and generates a second compare voltage that is applied to the first op amp, the first op amp comparing the first compare voltage to the second compare voltage to generate the bias voltage;
wherein the first reference transistor is a bipolar transistor having a base and a collector tied together and an emitter connected to the first reference transistor and to the first voltage divider;
wherein an emitter voltage of the first reference transistor is a voltage that falls with increasing absolute temperature,whereby the reference voltage includes the summing voltage that sums the complementary-to-absolute-temperature and proportional-to-absolute-temperature currents.
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Abstract
A bandgap reference voltage generator has a first stage that generates a first current that is complementary-to-absolute-temperature (Ictat) and a second stage that generates a current that is proportional-to-absolute-temperature (Iptat). The Ictat and Iptat currents are both forced through a summing resistor to generate a voltage that is relatively independent of temperature, since the Ictat and Iptat currents cancel out each other'"'"'s temperature dependencies. A PMOS output transistor drives current to an output load to maintain the load at the reference voltage. An op amp drives the gate of the PMOS output transistor and has inputs connected to emitters of PNP transistors in the second stage. A series of resistors generate the reference voltage between the PMOS output transistor and ground and drives bases of the PNP transistors and includes the summing resistor. Parasitic PNP transistors in an all-CMOS process are used. The generator operates with a 1-volt power supply.
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Citations
17 Claims
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1. A temperature-compensated reference-voltage generator comprising:
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a first stage that generates a complementary-to-absolute-temperature current that increases as temperature decreases; a second stage that generates a proportional-to-absolute-temperature current that increases as temperature increases; a summing resistor that receives both the complementary-to-absolute-temperature current from the first stage and the proportional-to-absolute-temperature current from the second stage, the summing resistor generating a summing voltage that is less dependent on temperature than either the complementary-to-absolute-temperature current or the proportional-to-absolute-temperature current; a final voltage divider, in the second stage, that generates a reference voltage that includes the summing voltage; an output transistor, coupled to the final voltage divider, for driving current to an output node, the output node being a node between the output transistor and the final voltage divider, the output node being driven by the output transistor to maintain the reference voltage on the output node; and a final op amp having an output that drives a gate of the output transistor, the final op amp having a first input connected to a first sensing node in the second stage, and a second input connected to a second sensing node in the second stage; wherein the first stage further comprises; a first reference transistor that generates a first reference voltage that is complementary-to-absolute-temperature; a first voltage divider coupled to the first reference voltage and generating a first compare voltage; a first op amp that receives the first compare voltage and generates a bias voltage; and a ctat current mirror transistor that receives the bias voltage from the first op amp, and generates the complementary-to-absolute-temperature current applied to the summing resistor, wherein the ctat current minor transistor is connected to the summing resistor; a first current minor transistor that receives the bias voltage from the first op amp and generates a first current; wherein the first current minor transistor is coupled to the first reference transistor and to the first voltage divider; a second current minor transistor that receives the bias voltage from the first op amp and generates a second current; a compare resistor that receives the second current and generates a second compare voltage that is applied to the first op amp, the first op amp comparing the first compare voltage to the second compare voltage to generate the bias voltage; wherein the first reference transistor is a bipolar transistor having a base and a collector tied together and an emitter connected to the first reference transistor and to the first voltage divider; wherein an emitter voltage of the first reference transistor is a voltage that falls with increasing absolute temperature, whereby the reference voltage includes the summing voltage that sums the complementary-to-absolute-temperature and proportional-to-absolute-temperature currents. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A voltage generator comprising:
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a first bipolar transistor connected to a first node; a first current minor transistor connected to the first node, and having a gate receiving a bias voltage; a first resistor connected between the first node and a first compare node; a second resistor connected to the first compare node; a second current minor transistor connected to a second node, and having a gate receiving the bias voltage; a third resistor connected to the second node; a first op amp receiving the first node and the second node as inputs, and generating the bias voltage as an output; a third current minor transistor connected to a summing node, and having a gate receiving the bias voltage; a summing resistor connected to the summing node; a first current transistor connected to a first sensing node; a first sensing bipolar transistor having a first terminal connected to the first sensing node, and a base terminal connected to a first base node; a second current transistor connected to a second sensing node; a second sensing bipolar transistor having a first terminal connected to the second sensing node, and a base terminal connected to the summing node; a second op amp receiving the first sensing node and the second sensing node as inputs, and generating a feedback voltage as an output; an output transistor having a gate receiving the feedback voltage from the second op amp, and connected to an output node; a fourth resistor coupled between the output node and the first base node; and a fifth resistor coupled between the first base node and the summing node, wherein the output node has a reference voltage that is generated by the voltage generator. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A compensating voltage generator circuit comprising:
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first stage means for generating a complementary-to-absolute-temperature current that increases as temperature decreases; second stage means for generating a proportional-to-absolute-temperature current that increases as temperature increases; summing resistor means, receiving both the complementary-to-absolute-temperature current from the first stage means and the proportional-to-absolute-temperature current from the second stage means, for generating a summing voltage that is less dependent on temperature than either the complementary-to-absolute-temperature current or the proportional-to-absolute-temperature current; final voltage divider means for generating a reference voltage that includes the summing voltage; output transistor means, coupled to the final voltage divider means, for driving current to an output node, the output node being a node between the output transistor means and the final voltage divider means, the output node being driven by the output transistor means to maintain the reference voltage on the output node; final operational amplifier means for driving a gate of the output transistor means, the final operational amplifier means having a first input connected to a first sensing node in the second stage means, and a second input connected to a second sensing node in the second stage means; first reference transistor means for generating a first reference voltage that is complementary-to-absolute-temperature; first voltage divider means, coupled to the first reference voltage, for generating a first compare voltage; first operational amplifier means, receiving the first compare voltage, for generating a bias voltage; ctat current minor transistor means, receiving the bias voltage, for generating the complementary-to-absolute-temperature current applied to the summing resistor means, wherein the ctat current minor transistor means is connected to the summing resistor means; first sensing transistor means for generating a first sensing voltage on the first sensing node in response to a base connected to a first intermediate node in the final voltage divider means; second sensing transistor means for generating a second sensing voltage on the second sensing node in response to a base connected to a base node between the final voltage divider means and the summing resistor means; whereby the reference voltage includes the summing voltage that sums the complementary-to-absolute-temperature and proportional-to-absolute-temperature currents.
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Specification