Power transistor feedback circuit with noise and offset compensation

• US 7,982,542 B1
• Filed: 02/26/2010
• Issued: 07/19/2011
• Est. Priority Date: 02/26/2010
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Sicard, Thierry
• Primary Examiner(s): NGUYEN, PATRICIA T
• Application Number:
  US12/714,112
• Time in Patent Office: 508 Days
• Field of Search: 330/290, 330/257, 330/302
• US Class Current: 330/290
• CPC Class Codes: H03F 2200/375 Circuitry to compensate the offset being present in an amplifier
• CPC Class Codes: H03F 2200/78 A comparator being used in a controlling circuit of an amplifier
• CPC Class Codes: H03F 2203/45296 the AAC comprising one or more discrete capacitive elements, e.g. a transistor coupled as capacitor
• CPC Class Codes: H03F 2203/45364 the AAC comprising multiple transistors parallel coupled at their gates and sources only, e.g. in a cascode dif amp, only those forming the composite common source transistor
• CPC Class Codes: H03F 2203/45418 the CMCL comprising a resistor addition circuit
• CPC Class Codes: H03F 2203/45594 the IC comprising one or more resistors, which are not biasing resistor
• CPC Class Codes: H03F 2203/45646 the LC comprising an extra current source
• CPC Class Codes: H03F 2203/45648 the LC comprising two current sources, which are not cascode current sources
• CPC Class Codes: H03F 3/4508 using bipolar transistors as the active amplifying circuit H03F3/45278 takes precedence
• CPC Class Codes: H03F 3/45569 Controlling the loading circuit of the differential amplifier

Abstract

A circuit comprises a first amplifier portion and a second amplifier portion. The first amplifier portion includes first and second transistors coupled together in a common-base configuration. A current mirror is coupled to the first and second transistors. A first filter is coupled between a first input and the first and second transistors. The second amplifier portion includes third and fourth transistors coupled together in a common-base configuration. First and second current sources are coupled to the third and fourth transistors. A second filter is coupled between a second input and the control electrodes of the third and fourth transistors, wherein the first and second filters are coupled together.

Claims

1. A circuit comprising:

a first amplifier portion comprising;

a first transistor having a first current electrode coupled to a first input, a second current electrode, and a control electrode;

a second transistor having a first current electrode coupled to the first input, a second current electrode, and a control electrode coupled to the control electrode of the first transistor;

a current mirror coupled to the second current electrodes of the first and second transistors; and

a first filter coupled between the first input and the control electrodes of the first and second transistors; and

a second amplifier portion comprising;

a third transistor having a first current electrode coupled to a second input, a second current electrode, and a control electrode coupled to the second current electrode of the third transistor;

a fourth transistor having a first current electrode coupled to the second input, a second current electrode coupled to an output terminal, and a control electrode coupled to the control electrode of the third transistor;

a first current source having a first terminal coupled to the third transistor, and a second terminal;

a second current source having a first terminal coupled to the fourth transistor, and a second terminal; and

a second filter coupled between the second input and the control electrodes of the third and fourth transistors, and wherein the first and second filters are coupled together.

2. The circuit of claim 1, wherein the first filter comprises:

a first capacitor having a first plate electrode coupled to the first input, and a second plate electrode coupled to the control electrodes of the first and second transistors; and

a first resistive element having a first terminal coupled to the control electrodes of the first and second transistors, and a second terminal coupled to the second current electrode of the second transistor.

3. The circuit of claim 2, wherein the second filter comprises:

a second capacitor having a first plate electrode coupled to the second input, and a second plate electrode coupled to the control electrodes of the third and fourth transistors; and

a second resistive element having a first terminal coupled to the control electrodes of the third and fourth transistors, and a second terminal coupled to the second terminal of the first resistive element.

4. The circuit of claim 1, wherein the current mirror comprises:

a fifth transistor having a first current electrode coupled to the second current electrode of the first transistor, a second current electrode, and a control electrode coupled to the second current electrode of the fifth transistor; and

a sixth transistor having a first current electrode coupled to the second current electrode of the second transistor, a second current electrode, and a control electrode coupled to the control electrode of the fifth transistor.

5. The circuit of claim 4, wherein the fifth and sixth transistors each further comprises a body terminal coupled to the first input.

6. The circuit of claim 1, further comprising a voltage reference source coupled between the second input and the second terminals of the first and second current sources.

7. The circuit of claim 6, wherein the voltage reference source comprises:

a diode having a first terminal coupled to the second input, and a second terminal; and

a zener diode having a first terminal coupled to the second terminal of the diode, and a second terminal coupled to the second terminals of the first and second current sources.

8. The circuit of claim 1, further comprising:

a seventh transistor having a first current electrode coupled to a first power supply voltage terminal, a second current electrode coupled to the first input, and a control electrode;

an eighth transistor having a first current electrode coupled to the second current electrode of the seventh transistor, a second current electrode, and a control electrode coupled to the output terminal;

a third resistive element having a first terminal coupled to the second current electrode of the eighth transistor, and a second terminal coupled to a second power supply voltage terminal; and

a high side switch transistor having a first current electrode coupled to the first power supply voltage terminal, a second current electrode coupled to the second input, and a control electrode.

9. The circuit of claim 8, wherein the seventh transistor is an N-channel transistor and the eighth transistor is a P-channel transistor.

10. A circuit comprising:

a first amplifier portion comprising;

a first transistor having a first current electrode coupled to a first input, a second current electrode, and a control electrode;

a second transistor having a first current electrode coupled to the first input, a second current electrode, and a control electrode coupled to the control electrode of the first transistor;

a current mirror coupled to the second current electrodes of the first and second transistors; and

a first filter coupled between the first input and the control electrodes of the first and second transistors;

a second amplifier portion comprising;

a third transistor having a first current electrode coupled to a second input, a second current electrode, and a control electrode coupled to the second current electrode of the third transistor;

a fourth transistor having a first current electrode coupled to the second input, a second current electrode coupled to an output terminal, and a control electrode coupled to the control electrode of the third transistor;

a first current source having a first terminal coupled to the third transistor, and a second terminal;

a second current source having a first terminal coupled to the fourth transistor, and a second terminal; and

a second filter coupled between the second input and the control electrodes of the third and fourth transistors, and wherein the first and second filters are coupled together; and

a third current source having a first terminal coupled to the second terminals of both the first and second current sources, and a second terminal coupled to a first power supply voltage terminal.

11. The circuit of claim 10, wherein the first filter comprises:

a first capacitor having a first plate electrode coupled to the first input, and a second plate electrode coupled to the control electrodes of the first and second transistors; and

a first resistive element having a first terminal coupled to the control electrodes of the first and second transistors, and a second terminal coupled to the second current electrode of the second transistor.

12. The circuit of claim 11, wherein the second filter comprises:

a second capacitor having a first plate electrode coupled to the second input, and a second plate electrode coupled to the control electrodes of the third and fourth transistors; and

a second resistive element having a first terminal coupled to the control electrodes of the third and fourth transistors, and a second terminal coupled to the second terminal of the first resistive element.

13. The circuit of claim 10, wherein the current mirror comprises:

a fifth transistor having a first current electrode coupled to the second current electrode of the first transistor, a second current electrode, and a control electrode coupled to the second current electrode of the fifth transistor; and

a sixth transistor having a first current electrode coupled to the second current electrode of the second transistor, a second current electrode, and a control electrode coupled to the control electrode of the fifth transistor.

14. The circuit of claim 13, wherein the fifth and sixth transistors each further comprises a body terminal coupled to the first input.

15. The circuit of claim 10, further comprising a voltage reference source coupled between the second input and the second terminals of the first and second current sources.

16. The circuit of claim 15, wherein the voltage reference source comprises:

a diode having a first terminal coupled to the second input, and a second terminal; and

a zener diode having a first terminal coupled to the second terminal of the diode, and a second terminal coupled to the second terminals of the first and second current sources.

17. The circuit of claim 10, further comprising:

a seventh transistor having a first current electrode coupled to a first power supply voltage terminal, a second current electrode coupled to the first input, and a control electrode;

an eighth transistor having a first current electrode coupled to the second current electrode of the seventh transistor, a second current electrode, and a control electrode coupled to the output terminal;

a third resistive element having a first terminal coupled to the second current electrode of the eighth transistor, and a second terminal coupled to a second power supply voltage terminal; and

a high side switch transistor having a first current electrode coupled to the first power supply voltage terminal, a second current electrode coupled to the second input, and a control electrode.

18. A circuit comprising:

a first amplifier portion comprising;

a first transistor having a first current electrode coupled to a first input, a second current electrode, and a control electrode;

a second transistor having a first current electrode coupled to the first input, a second current electrode, and a control electrode coupled to the control electrode of the first transistor;

a current mirror coupled to the second current electrodes of the first and second transistors;

a first capacitor having a first plate electrode coupled to the first input, and a second plate electrode coupled to the control electrodes of the first and second transistors; and

a first resistive element having a first terminal coupled to the control electrodes of the first and second transistors, and a second terminal coupled to the second current electrode of the second transistor; and

a second amplifier portion comprising;

a third transistor having a first current electrode coupled to a second input, a second current electrode, and a control electrode coupled to the second current electrode of the third transistor;

a fourth transistor having a first current electrode coupled to the second input, a second current electrode coupled to an output terminal, and a control electrode coupled to the control electrode of the third transistor;

a first current source having a first terminal coupled to the third transistor, and a second terminal;

a second current source having a first terminal coupled to the fourth transistor, and a second terminal;

a second capacitor having a first plate electrode coupled to the second input, and a second plate electrode coupled to the control electrodes of the third and fourth transistors; and

a second resistive element having a first terminal coupled to the control electrodes of the third and fourth transistors, and a second terminal coupled to the second terminal of the first resistive element.

19. The circuit of claim 18, further comprising:

a voltage reference source coupled between the second input and the second terminals of the first and second current sources; and

a third current source having a first terminal coupled to the second terminals of both the first and second current sources, and a second terminal coupled to a power supply voltage terminal.

20. The circuit of claim 18, wherein the current mirror comprises:

a fifth transistor having a first current electrode coupled to the second current electrode of the first transistor, a second current electrode, a control electrode coupled to the second current electrode of the fifth transistor, and a body terminal coupled to the first input; and

a sixth transistor having a first current electrode coupled to the second current electrode of the second transistor, a second current electrode, a control electrode coupled to the control electrode of the fifth transistor, and a body terminal coupled to the first input.