Differential filter with high common mode rejection ratio

• US 20040205424A1
• Filed: 09/05/2003
• Published: 10/14/2004
• Est. Priority Date: 09/06/2002
• Status: Abandoned Application

• Current Assignee: AJ Medical Devices, Inc.
• Original Assignee: AJ Medical Devices, Inc.
• Inventors: Garrett, Michael C.
• Application Number:
  US10/656,914
• Publication Number:
  US 20040205424A1
• Time in Patent Office: Days
• US Class Current: 714/700
• CPC Class Codes: H03F 3/45183 Long tailed pairs H03F3/4521, H03F3/45237 take precedence
• CPC Class Codes: H03F 3/45475 using IC blocks as the active amplifying circuit
• CPC Class Codes: H03F 3/45753 using switching means, e.g. sample and hold
• CPC Class Codes: H03F 3/45977 using switching means, e.g. sample and hold

Abstract

A differential amplifier (701) has an input for coupling to one or more signal sources (702). An offset error correction parameter input (704) is provided proximal to this input and serves to facilitate the reduction or elimination of undesired DC or low frequency offsets while further permitting a relatively large gain to be applied to the incoming signal without also amplifying considerable undesired DC/low frequency offset content.

Claims

1. A method of removing offsets to a signal comprising:

providing at least two signal inputs that correspond to a bio-metric parameter;

providing an error correction parameter;

combining at least one signal carried by the at least two signal inputs with the error correction parameter to provide a resultant error-corrected signal;

amplifying the resultant error-corrected signal to provide an amplified resultant error-corrected signal.

2. The method of claim 1 wherein providing an error correction parameter comprises providing a DC offset error correction parameter.

3. The method of claim 1 wherein providing an error correction parameter comprises providing a low frequency offset error correction parameter.

4. The method of claim 3 wherein providing a low frequency offset error correction parameter comprises providing a low frequency offset error correction parameter as corresponds to a frequency of less than 1 Hertz.

5. The method of claim 1 wherein amplifying the resultant error-corrected signal comprises amplifying the resultant error-corrected signal by at least a gain of 50.

6. The method of claim 1 wherein providing an error correction parameter comprises processing an earlier amplified resultant error-corrected signal.

7. The method of claim 6 wherein processing an earlier amplified resultant error-corrected signal comprises comparing the earlier amplified resultant error-corrected signal to a reference value.

8. The method of claim 7 wherein the reference value comprises a substantially fixed value.

9. The method of claim 8 wherein the reference value comprises a desired offset value to be maintained as a part of the amplified resultant error-corrected signal.

10. The method of claim 6 wherein processing an earlier amplified resultant error-corrected signal comprises processing an earlier amplified resultant error-corrected signal in a frequency selected manner.

11. The method of claim 10 wherein the frequency selected manner comprises at least one of:

low frequency passage;

high frequency passage;

narrow band frequency passage.

12. The method of claim 1 and further comprising combining a second signal carried by the at least two signal inputs with the error correction parameter to provide a second resultant error-corrected signal.

13. A bio-metric monitoring device amplifier comprising:

a power source;

a plurality of signal inputs;

an initial amplifier that operably couples to the power source and that receives a bio-metric signal as carried by the plurality of signal inputs, wherein the initial amplifier has a gain of at least 25.

14. The bio-metric monitoring device amplifier of claim 13 wherein the power source comprises a 1.5 volt battery.

15. The bio-metric monitoring device amplifier of claim 13 and further comprising an error correction parameter and wherein the initial amplifier is responsive to the error correction parameter.

16. The bio-metric monitoring device amplifier of claim 13 and further comprising an error correction parameter and a combiner that operably couples to receive the error correction parameter and at least one of the plurality of signal inputs.

17. The bio-metric monitoring device amplifier of claim 16 wherein the combiner provides an error-corrected output to the initial amplifier.

18. The bio-metric monitoring device amplifier of claim 13 and further comprising means for processing a resultant amplified signal from the initial amplifier to provide an error correction parameter.

19. The bio-metric monitoring device amplifier of claim 18 wherein the error correction parameter comprises at least one of:

a DC offset correction parameter;

a low frequency offset correction parameter.

20. A method comprising:

providing a differential amplifier having an input;

providing a signal;

substantially removing at least a DC component of the signal proximal to the input of the differential amplifier.

21. The method of claim 20 wherein substantially removing at least a DC component of the signal proximal to the input of the differential amplifier comprises substantially removing at least a DC component of the signal prior to provision to the input of the differential amplifier.

22. The method of claim 20 wherein substantially removing at least a DC component of the signal proximal to the input of the differential amplifier comprises substantially removing at least a DC component of the signal within the differential amplifier.

23. An apparatus comprising:

a differential amplifier having an input to facilitate coupling to a signal source;

an offset error correction parameter input disposed proximal to the input of the differential amplifier to avoid amplification of undesired offsets.

24. The apparatus of claim 23 wherein the signal source comprises a bio-metric signal source.

25. The apparatus of claim 23 and further comprising error correction means for using the error correction parameter to provide a resultant error-corrected signal.

26. The apparatus of claim 25 wherein the differential amplifier has an output that provides the resultant error-corrected signal as amplified by a gain.

27. The apparatus of claim 26 wherein the differential amplifier has an output that provides the resultant error-corrected signal as amplified by the gain and having a predetermined offset.

28. The apparatus of claim 27 wherein the predetermined offset comprises at least one of:

a DC offset;

a low frequency offset.

29. The apparatus of claim 27 wherein the predetermined offset comprises a non-zero predetermined offset.