Bias stabilizer circuit and method of operation

• US 6,411,154 B1
• Filed: 02/20/2001
• Issued: 06/25/2002
• Est. Priority Date: 02/20/2001
• Status: Expired due to Term

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: Mikulenka, Frantisek
• Primary Examiner(s): Callahan, Timothy P.
• Assistant Examiner(s): Luu, An T.
• Application Number:
  US09/785,750
• Time in Patent Office: 490 Days
• Field of Search: 327/530, 327/538, 327/540, 327/541-3, 327/138, 327/83, 327/378, 327/512, 327/513, 327/239, 327/256, 327/257-9, 323/311-317
• US Class Current: 327/530
• CPC Class Codes: G05F 3/205 Substrate bias-voltage generators for static stores G11C5/146

Abstract

A bias circuit (200, FIG. 2) includes a first bipolar junction transistor (BJT) (240), which provides, to an external transistor (204), a biasing voltage (294) equal to the first BJT'"'"'s base-emitter junction voltage plus a biasing voltage at the first BJT'"'"'s base (244). A current multiplying mirror circuit (250) senses a fraction of the first BJT'"'"'s collector current, and produces a current equal to the collector current. This mirror current flows through a second BJT (230). A voltage at the collector (232) of the second BJT is divided, producing the biasing voltage at the base (244) of the first BJT. This biasing voltage has a temperature coefficient with an opposite sign and a same magnitude as a temperature coefficient of the first BJT'"'"'s base-emitter junction voltage, resulting in a near zero temperature coefficient for the biasing voltage (294).

Claims

1. A bias circuit for biasing an external transistor, the bias circuit comprising:

a first bipolar junction transistor (BJT) having a first base-emitter junction voltage with a first temperature coefficient, and a first collector through which a first collector current flows;

a second BJT having a second base emitter junction voltage with a second temperature coefficient that is approximately equal to the first temperature coefficient, and a second collector through which a second collector current flows, wherein the second collector current is a duplicated version of the first collector current; and

a voltage divider circuit, coupled to divide a voltage at the second collector to provide a biasing voltage to a first base of the first BJT that has a third temperature coefficient with an opposite sign and a same magnitude as the first temperature coefficient.

2. The bias circuit as claimed in claim 1, further comprising:

a first circuit, coupled to the first collector of the first BJT, which senses a fraction of the first collector current and produces the duplicated version of the first collector current.

3. The bias circuit as claimed in claim 2, wherein the first collector includes multiple collector regions, wherein a fraction of the multiple collector regions is coupled to the first circuit, and at least one of a remainder of the multiple collector regions is connectable to a base of the external transistor.

4. The bias circuit as claimed in claim 3, wherein the first circuit comprises:

a third BJT having a third collector that is coupled to the second collector of the second BJT; and

a fourth BJT having a fourth collector that is coupled to the fraction of the multiple collector regions, and

wherein the third BJT has an emitter area with a size that is a multiple of a size of an emitter area of the fourth BJT, and wherein the multiple equals an inverse of the fraction of the multiple collector regions that are coupled to the fourth BJT.

5. The bias circuit as claimed in claim 4, wherein the first circuit further comprises a fifth BJT having a fifth base that is coupled to the fraction of the multiple collector regions, and an emitter that is coupled to a third base of the third BJT and a fourth base of the fourth BJT.

6. The bias circuit as claimed in claim 1, further comprising a pair of resistors, coupled to the second BJT, that provide a biasing voltage at a second base of the second BJT.

7. The bias circuit as claimed in claim 1, further comprising:

a voltage divider circuit, coupled to the second collector, which divides a voltage at the second collector to provide a biasing voltage to a first base of the first BJT, wherein the biasing voltage has a third temperature coefficient with an opposite sign and a same magnitude as the first temperature coefficient; and

an enable circuit, coupled to the voltage divider circuit, wherein an input signal to the enable circuit activates and deactivates the bias circuit.

8. The bias circuit as claimed in claim 1, wherein the first BJT and the second BJT are a part of an integrated circuit device.

9. A mobile communication unit comprising:

a first transistor for amplifying a signal, the first transistor including a first collector and a first base; and

a bias circuit including;

a second transistor that provides a biasing voltage to the first collector and a bias current to the first base, the second transistor having a second collector through which a second collector current flows, and a first base-emitter junction voltage with a first temperature coefficient,

a third transistor having a second base emitter junction voltage with a second temperature coefficient that is approximately equal to the first temperature coefficient, and a third collector through which a third collector current flows, wherein the third collector current is a duplicated version of the second collector current, and

a voltage divider circuit, coupled to divide a voltage at the third collector to provide a biasing voltage to a second base of the second transistor, wherein the biasing voltage has a third temperature coefficient with an opposite sign and a same magnitude as the first temperature coefficient.

10. The mobile communication unit as claimed in claim 9, further comprising:

a first circuit, coupled to the second collector, which senses a fraction of the second collector current and produces the duplicated version of the second collector current, and

wherein the second collector includes multiple collector regions, and a fraction of the multiple collector regions is coupled to the first circuit, and at least one of a remainder of the multiple collector regions is connectable to the first base of the first transistor.

11. The mobile communication unit as claimed in claim 10, wherein the first circuit comprises:

a fourth transistor having a fourth collector, a fourth base, and a fourth emitter, wherein the fourth collector is coupled to the third collector; and

a fifth transistor having a fifth collector that is coupled to the fraction of the multiple collector regions, a fifth emitter, and a fifth base, and

wherein the fourth transistor has an emitter area with a size that is a multiple of a size of an emitter area of the fifth transistor, and the multiple equals an inverse of the fraction of the multiple collector regions that is coupled to the fifth transistor.

12. The mobile communication unit as claimed in claim 11, wherein the first circuit further comprises a sixth transistor having a sixth base that is coupled to the fraction of the multiple collector regions, and a sixth emitter that is coupled to the fourth base of the fourth transistor and the fifth base of the fifth transistor.

13. The mobile communication unit as claimed in claim 9, wherein the voltage divider circuit includes a pair of resistors, coupled to the third transistor, that provide the biasing voltage.

14. The mobile communication unit as claimed in claim 9, further comprising:

an enable circuit, coupled to the voltage divider circuit, wherein an input signal to the enable circuit activates and deactivates the bias circuit.

15. A method for biasing an external transistor performed by a bias circuit, the method comprising:

sensing, by a first circuit, a fraction of a first current through a first collector of a first bipolar junction transistor (BJT), wherein the first BJT has a base-emitter junction voltage with a first temperature coefficient;

producing, by the first circuit, a second current that is approximately equal to the first current, wherein the second current flows through a second collector of a second BJT; and

dividing a second voltage at the second collector to provide a biasing voltage to the first BJT, wherein the biasing voltage has a second temperature coefficient with a same magnitude but an opposite sign from the first temperature coefficient.

16. The method as claimed in claim 15, wherein the first collector of the first BJT includes multiple collector regions, a fraction of the multiple collector regions is coupled to the first circuit, and at least one of a remainder of the multiple collector regions is connectable to a base of the external transistor, and wherein producing the second current comprises biasing a third BJT, which has an emitter area with a size that is a multiple of a size of an emitter area of a fourth BJT, and the multiple equals an inverse of the fraction of the multiple collector regions that are coupled to a fourth collector of the fourth BJT.

17. The method as claimed in claim 15, wherein the first BJT and the second BJT are of a same type, and producing the second current comprises biasing the second BJT so that the second current flows through the second collector, and the second voltage is established at the second collector.

18. The method as claimed in claim 15, further comprising activating and deactivating the bias circuit based on an input signal.