Bandgap voltage reference insensitive to voltage offset

• US 6,690,228 B1
• Filed: 12/11/2002
• Issued: 02/10/2004
• Est. Priority Date: 12/11/2002
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Chen, Jun, Hoon, Siew Kuok
• Primary Examiner(s): Callahan, Timothy P.
• Assistant Examiner(s): Luu, An T.
• Application Number:
  US10/316,340
• Time in Patent Office: 426 Days
• Field of Search: 327/538, 327/539, 327/540, 327/541, 327/543, 327/307, 323/312-316
• US Class Current: 327/538
• 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

Abstract

A bandgap reference circuit. The circuit includes a first current mirror having a first mirror transistor and a second mirror transistor. A holding circuit has an output adapted to control a current though the first current mirror by operating to maintain substantially equal the voltages at a first input thereof and at a second input thereof. A first bipolar transistor having an emitter, a base, and a collector, wherein the area of the emitter thereof has a predetermined size, is arranged to conduct a collector current from the first mirror transistor. A second bipolar transistor having an emitter, a base, and a collector, wherein the area of the emitter thereof has a size that is proportional to the size of the emitter area of the first bipolar transistor, is arranged to conduct a collector current from the second mirror transistor, the base thereof being connected to the collector thereof. A first resistor is provided, in series with the collector of the second bipolar transistor and the second mirror transistor. The base of the first bipolar transistor is coupled to a common connection node of the first resistor and the second mirror transistor to substantially reduce the effects of offset error in the holding circuit. The holding circuit may be an operational amplifier.

Claims

1. A bandgap reference circuit, comprising:

a first current mirror comprising a first mirror transistor and a second mirror transistor;

a holding circuit having an output adapted to control a current though the first current mirror by operating to maintain substantially equal the voltages at a first input thereof and at a second input thereof;

a first bipolar transistor having an emitter, a base, and a collector, wherein the area of the emitter thereof has a predetermined size, arranged to conduct a collector current from the first mirror transistor;

a second bipolar transistor having an emitter, a base, and a collector, wherein the area of the emitter thereof has a size that is proportional to the size of the emitter area of the first bipolar transistor, arranged to conduct a collector current from the second mirror transistor, the base thereof being connected to the collector thereof;

a first resistor in series with the collector of the second bipolar transistor and the second mirror transistor;

wherein the base of the first bipolar transistor is coupled to a common connection node of the first resistor and the second mirror transistor.

2. A bandgap reference circuit according to claim 1, wherein the holding circuit comprises an operational amplifier.

3. A bandgap reference circuit according to claim 1, further comprising:

a second resistor in parallel with the first resistor and the collector of the second bipolar transistor; and

a third resistor in parallel with the emitter and the collector of the first bipolar transistor.

4. A bandgap reference circuit according to claim 1, further comprising:

a second resistor;

a third bipolar transistor arranged to conduct a base-emitter current and having a base coupled to the first mirror transistor; and

a fourth bipolar transistor arranged to conduct a base-emitter current through the second resistor and having a base coupled to the first mirror transistor.

5. A bandgap reference circuit according to claim 1, wherein the holding circuit comprises a second current mirror, comprising:

a third mirror transistor adapted to conduct a mirror current substantially the same as the current through the second mirror transistor;

a fourth mirror transistor coupled to the third mirror transistor to mirror the mirror current therethrough, and coupled between the first mirror transistor and the first bipolar transistor; and

a fifth mirror transistor coupled to the third mirror transistor to mirror the mirror current therethrough, and coupled between the second mirror transistor and the second bipolar transistor.

6. A bandgap reference circuit according to claim 1, wherein the holding circuit comprises a second current mirror coupled between the first current mirror and the first and second bipolar transistors, and adapted to mirror a current substantially the same as the current through the second mirror transistor thorough the first mirror transistor.