Bandgap reference circuit

• US 5,796,244 A
• Filed: 07/11/1997
• Issued: 08/18/1998
• Est. Priority Date: 07/11/1997
• Status: Expired due to Term

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Vanguard International Semiconductor Corporation
• Inventors: Chen, Yun Sheng, Lin, Ming-Zen
• Primary Examiner(s): BERHANE, ADOLF D
• Application Number:
  US08/893,641
• Time in Patent Office: 403 Days
• Field of Search: 323/313, 323/314, 323/907, 327/513, 327/539
• US Class Current: 323/313
• CPC Class Codes: G05F 3/30 Regulators using the difference between the base-emitter voltages of two bipolar transistors operating at different current densities G05F3/26 takes precedence
• CPC Class Codes: Y10S 323/907 Temperature compensation of semiconductor

Abstract

A voltage reference circuit that will remain constant and independent of changes in the operating temperature that is correlated to the bandgap voltage of silicon is described. The voltage reference circuit will be incorporated within an integrated circuit and will minimize currents into the substrate. The bandgap voltage reference circuit has a bandgap voltage referenced generator that will generate a first referencing voltage having a first temperature coefficient, and a compensating voltage generator that will generate a second referencing voltage having a second temperature coefficient. The second temperature coefficient is approximately equal and of opposite sign to the first temperature coefficient. A voltage summing circuit will sum the first referencing voltage and the second referencing voltage to create the temperature independent voltage. A voltage biasing circuit will couple a bias voltage to the bandgap voltage referenced generating means to bias the bandgap voltage referenced generator to generate the first referencing voltage. The voltage biasing circuit has a first MOSFET configured as first diode having an anode coupled to the power supply voltage source, and a second MOSFET configured as second diode having an anode coupled to the source of the first MOSFET and a cathode coupled to the ground reference point. The biasing voltage is developed at the connection of the cathode of the first diode and the anode of the second diode and said biasing voltage has a value a voltage drop across said second diode.

Claims

1. A reference voltage source circuit that is coupled between a power supply voltage source, a ground reference point and a substrate biasing voltage source, is incorporated within an integrated circuit, and is correlated to the bandgap of silicon to provide a temperature independent voltage while minimizing currents flowing to said substrate biasing voltage source, comprising:

a) a bandgap voltage referenced generating means to generate a first referencing voltage having a first temperature coefficient;

b) a compensating voltage generating means to generate a second referencing voltage having a second temperature coefficient, wherein the second temperature coefficient is approximately equal and of opposite sign to said first temperature coefficient;

c) a voltage summing means coupled to the bandgap voltage referenced voltage generating means and the compensating voltage generating means to sum the first referencing voltage and the second referencing voltage to create the temperature independent voltage; and

d) a voltage biasing means to couple a bias voltage to the bandgap voltage referenced generating means to bias said bandgap voltage referenced generating means so as to generate the first referencing voltage.

2. The reference voltage source of claim 1 wherein said bandgap voltage referenced generating means comprises:

a) a first constant current source having a first current input terminal coupled to the power supply voltage source and a first current output terminal to transfer a first constant current;

b) a second constant current source having a second current input terminal coupled to the power supply voltage source and a second current output terminal to transfer a second constant current;

c) a first resistor having a first terminal connected to the first current output terminal, and a second terminal;

d) a first bipolar junction transistor having an emitter connected to the second terminal of the resistor, a collector connected to the substrate biasing voltage source, and a base coupled to the voltage biasing means to receive said bias voltage and wherein said first bandgap referencing voltage is developed at said emitter and the first terminal of said first resistor; and

e) a second bipolar junction transistor having an emitter connected to the second current output terminal, a collector connected to the substrate bias voltage source, and a base connected to the biasing voltage means to receive said bias voltage wherein said second bandgap referencing voltage is developed at said emitter,

f) an operational amplifier having a noninverting input connected to the first terminal of the first resistor to receive the first bandgap referencing voltage, an inverting terminal connected to the emitter of the second bipolar junction transistor to receive the second bandgap referencing voltage, an amplifying means to amplify the difference between the first bandgap referencing voltage and the second bandgap referencing voltage, and an amplifier output terminal containing said difference voltage which is the difference in a voltage developed between the bases and the emitters of the first bipolar junction transistor and the second bipolar junction transistor added to the voltage developed between the first and second terminal of the first resistor.

3. The reference voltage source circuit of claim 2 wherein the first constant current source comprises a first MOSFET of a second conductivity type having a source connected to the power supply voltage source, a drain connected to the first current output terminal, and a gate connected to the amplifier output terminal, whereby said difference voltage is a bias voltage to the first MOSFET of the second conductivity type to create said first constant current.

4. The reference voltage source circuit of claim 2 wherein the second constant current source comprises a second MOSFET of a second conductivity type having a source connected to the power supply voltage source, a drain connected to the second current output terminal, and a gate connected to the amplifier output terminal, whereby said difference voltage is a bias voltage to the second MOSFET of the second conductivity type to create said second constant current.

5. The reference voltage source circuit of claim 1 wherein said voltage biasing means comprises:

a) a first MOSFET of a first conductivity type having a gate and a drain coupled to the power supply voltage source and a source, whereby said first MOSFET of the first conductivity type is configured as first diode having an anode coupled to the power supply voltage source; and

b) a second MOSFET of a first conductivity type having a gate and a drain coupled to the source of the first MOSFET of the conductivity type and a source coupled to the ground reference point, whereby said second MOSFET of the first conductivity type is configured as second diode having an anode coupled to the source of the first MOSFET of the first conductivity type and a cathode coupled to the ground reference point.

6. The reference voltage source circuit of claim 5 wherein the biasing voltage is developed at the connection of the cathode of the first diode and the anode of the second diode and said biasing voltage has a value a voltage drop across said second diode.

7. The reference voltage source circuit of claim 1 wherein the voltage summing means comprises:

a third MOSFET of the second conductivity type having a source connected to the power supply voltage source, a gate connected to the amplifier output terminal to receive the difference voltage, and a drain connected to external circuitry to provide said temperature independent voltage.

8. The reference voltage source circuit of claim 1 wherein the compensating voltage means comprises:

a) a third bipolar junction transistor having a collector connected to the substrate bias voltage source, a base connected to the ground reference point, and an emitter; and

b) a second resistor connected between the drain of the third MOSFET of the second conductivity type and the emitter of the third bipolar junction transistor, whereby a current generated in the voltage summing means causes a voltage to be developed across said second resistor and said temperature independent voltage is the sum of said voltage developed across said second resistor summed with the voltage developed between the base and the emitter of said third bipolar junction transistor.

9. A reference voltage source circuit that is coupled between a power supply voltage source, a ground reference point and a substrate biasing voltage source, is incorporated within an integrated circuit, and is correlated to the bandgap of silicon to provide a temperature independent voltage to a voltage reference terminal while minimizing currents flowing to said substrate biasing voltage source, comprising:

a) a bandgap voltage referenced generating means to generate a first referencing voltage having a first temperature coefficient wherein said bandgap voltage referenced generating means comprises;

a first constant current source having a first current input terminal coupled to the power supply voltage source and a first current output terminal to transfer a first constant current,

a second constant current source having a second current input terminal coupled to the power supply voltage source and a second current output terminal to transfer a second constant current,

a first resistor having a first terminal connected to the first current output terminal, and a second terminal,

a first bipolar junction transistor having an emitter connected to the second terminal of the resistor, a collector connected to the substrate biasing voltage source, and a base coupled to the voltage biasing means to receive said bias voltage and wherein said first bandgap referencing voltage is developed at said emitter added to a voltage developed between the first and second terminal of said first resistor,

a second bipolar junction transistor having an emitter connected to the second current output terminal, a collector connected to the substrate bias voltage source, and a base connected to the biasing voltage means to receive said bias voltage wherein said second bandgap referencing voltage is developed at said emitter, and

an operational amplifier having a noninverting input connected to the first terminal of the first resistor to receive the first bandgap referencing voltage, an inverting terminal connected to the emitter of the second bipolar junction transistor to receive the second bandgap referencing voltage, an amplifying means to amplify the difference between the first bandgap referencing voltage and the second bandgap referencing voltage, and an amplifier output terminal containing said difference voltage which is the difference in a voltage developed between the bases and the emitters of the first bipolar junction transistor and the second bipolar junction transistor added to the voltage developed between the first and second terminal of said first resistor;

b) a compensating voltage generating means to generate a second referencing voltage having a second temperature coefficient, wherein the second temperature coefficient is approximately equal and of opposite sign to said first temperature coefficient, wherein the compensating voltage means comprises;

a third bipolar junction transistor having a collector connected to the substrate bias voltage source, a base connected to the ground reference point, and an emitter; and

a second resistor connected between the voltage reference terminal and the emitter of the third bipolar junction transistor, whereby a current causes a voltage to be developed across said second resistor and said temperature independent voltage is the sum of said voltage developed across said second resistor summed with the voltage developed between the base and the emitter of said third bipolar junction transistor;

c) a voltage summing means coupled to the bandgap voltage referenced voltage generating means and the compensating voltage generating means to sum the first referencing voltage and the second referencing voltage to create the temperature independent voltage, wherein the voltage summing means comprises;

a first MOSFET of a second conductivity type having a source connected to the power supply voltage source, a gate connected to the amplifier output terminal to receive the difference voltage, and a drain connected to second resistor to provide the current to be transferred through said second resistor; and

d) a voltage biasing means to couple a bias voltage to the bandgap voltage referenced generating means to bias said bandgap voltage referenced generating means so as to generate the first referencing voltage, wherein said voltage biasing means comprises;

a first MOSFET of a first conductivity type having a gate and a drain coupled to the power supply voltage source and a source, whereby said first MOSFET of the first conductivity type is configured as first diode having an anode coupled to the power supply voltage source; and

a second MOSFET of the first conductivity type having a gate

and a drain coupled to the source of the first MOSFET of the conductivity type and a source coupled to the ground reference point, whereby said second MOSFET of the first conductivity type is configured as second diode having an anode coupled to the source of the first MOSFET of the first conductivity type and a cathode coupled to the ground reference point.

10. The reference voltage source circuit of claim 9 wherein the biasing voltage is developed at the connection of the cathode of the first diode and the anode of the second diode and said biasing voltage has a value a voltage drop across said second diode.

11. The reference voltage source circuit of claim 9 wherein the first constant current source comprises a second MOSFET of the second conductivity type having a source connected to the power supply voltage source, a drain connected to the first current output terminal, and a gate connected to the amplifier output terminal, whereby said difference voltage is a bias voltage to the second MOSFET of the second conductivity type to create said first constant current.

12. The reference voltage source circuit of claim 9 wherein the second constant current source comprises a third MOSFET of a second conductivity type having a source connected to the power supply voltage source, a drain connected to the second current output terminal, and a gate connected to the amplifier output terminal, whereby said difference voltage is a bias voltage to the third MOSFET of the second conductivity type to create said second constant current.

13. A bandgap reference circuit that is coupled between a power supply voltage source, a ground reference point and a substrate biasing voltage source, is incorporated within an integrated circuit, and is correlated to the bandgap of silicon to provide a temperature independent voltage to a voltage reference terminal while minimizing currents flowing to said substrate biasing voltage source, comprising:

a) a first bipolar junction transistor and a second bipolar junction transistor, wherein said temperature independent biasing voltage is a function of a difference in a voltage developed between a base and an emitter of each of the first bipolar junction transistor and the second bipolar junction transistor, and wherein a collector of each of the first and second bipolar junction transistors are connected to the substrate;

b) a first MOSFET of a first conductivity type and a second MOSFET of the first conductivity type each having a source and a drain connected together to respectively form a first diode and second diode, wherein said first and second diodes are interconnected serially between the power supply voltage source and the ground reference point whereby an interconnection point between said first and second diodes is connected to the base of each of the first and second bipolar junction transistor;

c) a first resistor having a first terminal connected to the emitter of the first bipolar junction transistor to develop the difference in the voltage developed between the base and emitter of each of the first and second bipolar junction transistors;

d) a first MOSFET of a second conductivity type and a second MOSFET of the second conductivity type, wherein the drain of the first MOSFET of the second conductivity type is connected to a second terminal of the first resistor and the drain of the second MOSFET of the second conductivity type is connected to an emitter of the second bipolar junction transistor, and wherein the first and second MOSFET'"'"'s of the second conductivity type are configured to function respectively as a first and second constant current source, whereby each of the first and second constant current sources will provide an identical current to the first and second bipolar junction transistors;

e) an operational amplifier having a noninverting input connected to the second terminal of the first resistor, an inverting input connected to the emitter of the second bipolar junction transistor, and an output that provides an output voltage that is an amplified version of the difference in the voltage developed between the base and emitter of each of the first and second bipolar junction transistors, and wherein said output is connected to a gate of each of the first and second MOSFET'"'"'s of the second conductivity type to control the magnitude of each of the constant currents form the first and second current sources;

f) a third MOSFET of the second conductivity type having a gate connected to the output of the operational amplifier, a source connected to the power supply voltage source, and a drain coupled to said voltage reference terminal, whereby said third MOSFET of the second conductivity type is configured to provide a third constant current from said drain;

g) a second resistor coupled to the voltage reference terminal to develop a voltage that is a function of the is the amplified version of the difference in the voltage developed between the base and emitter of each of the first and second bipolar junction transistors as a result of the third constant current; and

h) a third bipolar junction transistor having an emitter connected to the second resistor, a base connected to the ground reference point and a collector connected to the substrate biasing voltage source, whereby the temperature independent voltage is the sum of the voltage developed across the second resistor and the a voltage developed between the base and the emitter of said third bipolar junction transistor.