Differential filter with gyrator

• US 6,184,747 B1
• Filed: 05/13/1999
• Issued: 02/06/2001
• Est. Priority Date: 05/13/1999
• Status: Expired due to Fees

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell International Inc.
• Inventors: Maile, Keith R., Helgeson, Michael A.
• Primary Examiner(s): TON, MY TRANG
• Application Number:
  US09/311,105
• Time in Patent Office: 635 Days
• Field of Search: 327/551, 327/552, 327/553, 327/555, 327/556, 327/557, 327/558, 327/559, 330/303, 330/306, 455/307, 455/213
• US Class Current: 327/552
• CPC Class Codes: H03H 11/08 using gyrators

Abstract

A differential gyrator based filter is disclosed that preferably has a first gyrator connected to the positive input signal of the differential input signal and a second gyrator connected to the negative input signal of the differential input signal. A load capacitor is connected between the load terminals of the first gyrator and second gyrator, which minimizes the total load capacitance required for the gyrator based filter. This implementation is believed to increase the overall density, reliability, yield, signal-to-noise ratio and dynamic range of the gyrator based filter and related circuitry.

Claims

1. A differential gyrator filter for receiving a differential mode input signal comprising:

load means having an admittance; and

a differential gyrator having a positive input terminal and a negative input terminal with an input impedance therebetween for receiving the differential mode input signal, said differential gyrator coupled to said load means and providing an input impedance that is proportional to the admittance of said load means.

2. A differential filter having a positive filter input terminal and a negative filter input terminal, comprising:

first capacitance means having a first terminal and a second terminal;

second capacitance means having a first terminal and a second terminal;

first gyrator means having an input terminal and a load terminal, the input terminal of the first gyrator means coupled to the positive filter input terminal of the filter, and the load terminal of the first gyrator means coupled to the first terminal of said first capacitance means; and

second gyrator means having an input terminal and a load terminal, the input terminal of the second gyrator means coupled to the negative filter input terminal of the filter, and the load terminal of the second gyrator means coupled to the first terminal of said second capacitance means;

said second terminal of said first capacitance means and said second terminal of said second capacitance means coupled to a reference voltage.

3. A differential filter according to claim 2, wherein the reference voltage is ground.

4. A differential filter having a positive filter input terminal and a negative filter input terminal, comprising:

capacitance means having a first terminal and a second terminal;

first gyrator means having an input terminal and a load terminal, the input terminal of the first gyrator means coupled to the positive filter input terminal of the filter, and the load terminal of the first gyrator means coupled to the first terminal of said capacitance means; and

second gyrator means having an input terminal and a load terminal, the input terminal of the second gyrator means coupled to the negative filter input terminal of the filter, and the load terminal of the second gyrator means coupled to the second terminal of said capacitance means.

5. A filter according to claim 4, wherein the first gyrator means includes:

a first differential amplifier having a positive input terminal, a negative input terminal, a positive output terminal and a negative output terminal;

a second differential amplifier having a positive input terminal, a negative input terminal, a positive output terminal and a negative output terminal;

the positive input terminal of the first differential amplifier of the first gyrator means and the negative output terminal of the second differential amplifier of the first gyrator means are coupled to the input terminal of the first gyrator means;

the negative input terminal of the first differential amplifier of the first gyrator means is coupled to the positive output terminal of the second differential amplifier of the first gyrator means;

the positive output terminal of the first differential amplifier of the first gyrator means is coupled to the positive input terminal of the second differential amplifier of the first gyrator means; and

the negative output terminal of the first differential amplifier of the first gyrator means is coupled to the negative input terminal of the second differential amplifier of the first gyrator means.

6. A filter according to claim 5, wherein said capacitance means includes:

a first capacitor having a first terminal and a second terminal; and

a second capacitor having a first terminal and a second terminal.

7. A filter according to claim 6, wherein the positive output terminal of the first differential amplifier of the first gyrator means and the positive input terminal of the second differential amplifier of the first gyrator means are coupled to the first terminal of the first capacitor.

8. A filter according to claim 7, wherein the negative output terminal of the first differential amplifier of the first gyrator means and the negative input terminal of the second differential amplifier of the first gyrator means are coupled to the first terminal of the second capacitor.

9. A filter according to claim 8, wherein the second gyrator means includes:

a first differential amplifier having a positive input terminal, a negative input terminal, a positive output terminal and a negative output terminal;

a second differential amplifier having a positive input terminal, a negative input terminal, a positive output terminal and a negative output terminal;

the positive input terminal of the first differential amplifier of the second gyrator means and the negative output terminal of the second differential amplifier of the second gyrator means are coupled to the input terminal of the second gyrator means;

the negative input terminal of the first differential amplifier of the second gyrator means is coupled to the positive output terminal of the second differential amplifier of the second gyrator means;

the positive output terminal of the first differential amplifier of the second gyrator means is coupled to the positive input terminal of the second differential amplifier of the second gyrator means; and

the negative output terminal of the first differential amplifier of the second gyrator means is coupled to the negative input terminal of the second differential amplifier of the second gyrator means.

10. A filter according to claim 9, wherein the positive output terminal of the first differential amplifier of the second gyrator means and the positive input terminal of the second differential amplifier of the second gyrator means are coupled to the second terminal of the first capacitor.

11. A filter according to claim 10, wherein the negative output terminal of the first differential amplifier of the second gyrator means and the negative input terminal of the second differential amplifier of the second gyrator means are coupled to the second terminal of the second capacitor.

12. A filter according to claim 11, further comprising a positive filter output terminal and a negative filter output terminal.

13. A filter according to claim 12, wherein the negative input terminal of the first differential amplifier of the first gyrator means and the positive output terminal of the second differential amplifier of the first gyrator means are coupled to the positive filter output terminal.

14. A filter according to claim 13, wherein the negative input terminal of the first differential amplifier of the second gyrator means and the positive output terminal of the second differential amplifier of the second gyrator means are coupled to the negative filter output terminal.

15. A filter according to claim 14, further comprising a first filter capacitor element coupled between the input terminal of the first gyrator means and the positive filter output terminal of the filter.

16. A filter according to claim 15, further comprising a second capacitor element coupled between the input terminal of the second gyrator means and the negative filter output terminal of the filter.

17. A filter according to claim 16, further comprising a third capacitor element coupled between the input terminal of the first gyrator means and the input terminal of the second gyrator means.

18. A filter according to claim 16, further comprising a fourth capacitor element coupled between the positive filter output terminal and the negative filter output terminal.

19. A filter according to claim 18, further comprising:

a first resistor element coupled between the positive filter input terminal and the input terminal of the first gyrator means; and

a second resistor element coupled between the negative filter input terminal and the input terminal of the second gyrator means.

20. A filter having a number of cascaded filter stages, wherein each filter stage has a positive filter input terminal and a negative filter input terminal, each filter stage comprising:

one or more capacitors, each having a first terminal and a second terminal;

a first gyrator having an input terminal, an output terminal and one or more load terminals, the input terminal of the first gyrator coupled to the positive filter input terminal of the corresponding filter stage, and the one or more load terminals of the first gyrator coupled to the first terminals of the one or more capacitors;

a second gyrator having an input terminal, an output terminal and one or more load terminals, the input terminal of the second gyrator coupled to the negative filter input terminal of the corresponding filter stage, and the one or more load terminals of the second gyrator coupled to the second load terminals of the one or more capacitors; and

the output terminal of the first gyrator and the output terminal of the second gyrator being coupled to the positive filter input terminal and the negative filter input terminal, respectively, of the next succeeding filter stage.

21. A filter according to claim 20, wherein each filter stage further includes a first filter capacitor element coupled between the input terminal of the first gyrator and the positive filter input terminal of the next succeeding filter stage, and a second filter capacitor element coupled between the input terminal of the second gyrator and the negative filter input terminal of the next succeeding filter stage.

22. A filter according to claim 21, wherein each filter stage further includes a third capacitor element coupled between the input terminal of the first gyrator and the input terminal of the second gyrator.

23. A filter according to claim 22, further comprising:

a first resistor element coupled between the positive filter input terminal of a first filter stage and the input terminal of the first gyrator; and

a second resistor element coupled between the negative filter input terminal of the first filter stage and the input terminal of the second gyrator.

24. A filter according to claim 23, further comprising a third resistor element coupled between the output terminal of the first gyrator and the output terminal of the second gyrator of a last filter stage.

25. A filter according to claim 23, wherein the filter is fabricated using a CMOS process.

26. A differential filter having a positive filter input terminal and a negative filter input terminal, comprising:

capacitance means having a first terminal and a second terminal;

first gyrator means having an input terminal and a load terminal, the input terminal of the first gyrator means coupled to the positive filter input terminal of the filter, and the load terminal of the first gyrator means coupled to the first terminal of said capacitance means, said first gyrator means including;

a first differential amplifier having a positive input terminal, a negative input terminal, a positive output terminal and a negative output terminal;

a second differential amplifier having a positive input terminal, a negative input terminal, a positive output terminal and a negative output terminal;

the positive input terminal of the first differential amplifier of the first gyrator means and the negative output terminal of the second differential amplifier of the first gyrator means are coupled to the input terminal of the first gyrator means;

the negative input terminal of the first differential amplifier of the first gyrator means is coupled to the positive output terminal of the second differential amplifier of the first gyrator means;

the positive output terminal of the first differential amplifier of the first gyrator means is coupled to the positive input terminal of the second differential amplifier of the first gyrator means;

the negative output terminal of the first differential amplifier of the first gyrator means is coupled to the negative input terminal of the second differential amplifier of the first gyrator means;

second gyrator means having an input terminal and a load terminal, the input terminal of the second gyrator means coupled to the negative filter input terminal of the filter, and the load terminal of the second gyrator means coupled to the second terminal of said capacitance means, said second gyrator means including;

a first differential amplifier having a positive input terminal, a negative input terminal, a positive output terminal and a negative output terminal;

a second differential amplifier having a positive input terminal, a negative input terminal, a positive output terminal and a negative output terminal;

the positive input terminal of the first differential amplifier of the second gyrator means and the negative output terminal of the second differential amplifier of the second gyrator means are coupled to the input terminal of the second gyrator means;

the negative input terminal of the first differential amplifier of the second gyrator means is coupled to the positive output terminal of the second differential amplifier of the second gyrator means;

the positive output terminal of the first differential amplifier of the second gyrator means is coupled to the positive input terminal of the second differential amplifier of the second gyrator means; and

the negative output terminal of the first differential amplifier of the second gyrator means is coupled to the negative input terminal of the second differential amplifier of the second gyrator means.

27. A filter according to claim 26, wherein said capacitance means includes:

a first capacitor having a first terminal and a second terminal; and

a second capacitor having a first terminal and a second terminal.

28. A filter according to claim 27, wherein:

the positive output terminal of the first differential amplifier of the first gyrator means and the positive input terminal of the second differential amplifier of the first gyrator means are coupled to the first terminal of the first capacitor;

the negative output terminal of the first differential amplifier of the first gyrator means and the negative input terminal of the second differential amplifier of the first gyrator means are coupled to the first terminal of the second capacitor;

the positive output terminal of the first differential amplifier of the second gyrator means and the positive input terminal of the second differential amplifier of the second gyrator means are coupled to the second terminal of the first capacitor; and

the negative output terminal of the first differential amplifier of the second gyrator means and the negative input terminal of the second differential amplifier of the second gyrator means are coupled to the second terminal of the second capacitor.

29. A differential filter having a positive filter input terminal and a negative filter input terminal comprising:

capacitance means having at least two first terminals and at least two second terminal;

first gyrator means having an input terminal and at least two load terminals, the input terminal of the first gyrator means coupled to the positive filter input terminal of the filter, and each of the at least two load terminals of the first gyrator means coupled to a corresponding one of the at least two first terminals of said capacitance means; and

second gyrator means having an input terminal and at least two load terminals, the input terminal of the second gyrator means coupled to the negative filter input terminal of the filter, and each of the at least two load terminals of the second gyrator means coupled to a corresponding one of the at least two second terminals of said capacitance means.