초록 ▼

This disclosure describes a chopper stabilized instrumentation amplifier. The amplifier is configured to achieve stable measurements at low frequency with very low power consumption. The instrumentation amplifier uses a differential architecture and a mixer amplifier to substantially eliminate noise

This disclosure describes a chopper stabilized instrumentation amplifier. The amplifier is configured to achieve stable measurements at low frequency with very low power consumption. The instrumentation amplifier uses a differential architecture and a mixer amplifier to substantially eliminate noise and offset from an output signal produced by the amplifier. Dynamic limitations, i.e., glitching, that result from chopper stabilization at low power are substantially eliminated through a combination of chopping at low impedance nodes within the mixer amplifier and feedback. The signal path of the amplifier operates as a continuous time system, providing minimal aliasing of noise or external signals entering the signal pathway at the chop frequency or its harmonics. The amplifier can be used in a low power system, such as an implantable medical device, to provide a stable, low-noise output signal.

대표청구항 ▼

The invention claimed is: 1. A chopper-stabilized instrumentation amplifier comprising: a first modulator that modulates an amplitude of an input signal at a clock frequency to produce a modulated signal; a mixer amplifier that amplifies the modulated signal to produce an amplified signal and demod

The invention claimed is: 1. A chopper-stabilized instrumentation amplifier comprising: a first modulator that modulates an amplitude of an input signal at a clock frequency to produce a modulated signal; a mixer amplifier that amplifies the modulated signal to produce an amplified signal and demodulates an amplitude of the amplified signal at the clock frequency to produce an output signal; an input capacitor that couples the modulated signal to an input of the mixer amplifier; a second modulator that modulates an amplitude of the output signal at the clock frequency to produce a modulated output signal; and a feedback path that applies the modulated output signal as a feedback signal to the modulated signal at a node between the input capacitor and the input of the mixer amplifier via a feedback capacitor. 2. The amplifier of claim 1, wherein the mixer amplifier is a differential input mixer amplifier, and the input signal is a differential input signal, wherein the feedback capacitor includes first and second feedback capacitors and wherein the input capacitor includes first and second input capacitors, and wherein the node includes a first node between the first input capacitor and a first input of the mixer amplifier and a second node between the second input capacitor and a second input of the mixer amplifier, wherein the feedback path includes a first feedback path branch coupled to the first node via the first feedback capacitor and a second feedback path branch coupled to the second node via the second feedback capacitor, and wherein the second modulator includes a modulator in the first feedback path branch and a modulator in the second feedback path branch that modulate the amplitude of the output signal out of phase with one another. 3. The amplifier of claim 1, wherein a gain of the mixer amplifier is at least partially dependent on a ratio of a capacitance value of the feedback capacitor to a capacitance value of the input capacitor. 4. The amplifier of claim 1, wherein the feedback path is a first feedback path and the feedback capacitor is a first feedback capacitor, the amplifier further comprising: an integrator that integrates the output signal; a third modulator that modulates the integrated output signal at the clock frequency to produce a second feedback signal; and a second feedback path that applies the second feedback signal to the modulated signal at the node between the input capacitor and the input of the mixer amplifier via a second feedback capacitor. 5. The amplifier of claim 4, wherein the mixer amplifier is a differential input mixer amplifier, the input signal is a differential input signal, the second feedback path includes a first feedback path branch coupled to a first input of the mixer amplifier and a second Feedback path branch coupled to a second input of the mixer amplifier, and wherein the third modulator includes a modulator in the first feedback path branch and a modulator in the second feedback path branch that modulate the amplitude of the integrated output signal out of phase with one another. 6. The amplifier of claim 5, wherein each of the first and second feedback path branches of the second feedback path includes a feedback path branch capacitor, and wherein the second feedback path is dominant at frequencies lower than a high pass cutoff frequency, and the first feedback path is dominant at frequencies above the high pass cutoff frequency. 7. The amplifier of claim 1, wherein the mixer amplifier is a differential input mixer amplifier, and the input signal is a differential input signal, wherein the feedback capacitor includes first and second feedback capacitors and wherein the input capacitor includes first and second input capacitors, and wherein the node includes a first node between the first input capacitor and a first input of the mixer amplifier and a second node between the second input capacitor and a second input of the mixer amplifier, the amplifier further comprising a second feedback path including a first feedback path branch that couples an output of the mixer amplifier to a first input of the first modulator via a first switched capacitor, and a second feedback path branch that couples the output of the mixer amplifier to a second input of the first modulator via a second switched capacitor. 8. The amplifier of claim 7, wherein each of the first and second switched capacitors is configured to apply a scaled compensatory charge to a respective one of the input capacitors. 9. The amplifier of claim 1, further comprising a power source to power the amplifier, wherein the power source delivers less than approximately 2.0 microamps of electrical current to the amplifier during operation, and delivers a voltage of less than approximately 2.0 volts to the circuit. 10. The amplifier of claim 1, wherein the input signal has a frequency of less than or equal to approximately 1.0 Hz. 11. The amplifier of claim 1, wherein the mixer amplifier comprises an integrator that integrates the demodulated signal to produce the output signal. 12. A physiological sensing device comprising: a physiological sensor that generates an input signal indicative of a physiological condition; and a chopper-stabilized instrumentation amplifier comprising: a first modulator that modulates an amplitude of the input signal at a clock frequency to produce a modulated signal; a mixer amplifier that amplifies the modulated signal to produce an amplified signal and demodulates the amplified signal at the clock frequency to produce an output signal; an input capacitor that couples the modulated signal to an input of the mixer amplifier; a second modulator that modulates an amplitude of the output signal at the clock frequency to produce a modulated output signal; and a feedback path that applies the modulated output signal as a feedback signal to the modulated signal at a node between the input capacitor and an input of the mixer amplifier via a feedback capacitor. 13. The device of claim 12, wherein the mixer amplifier is a differential input mixer amplifier, and the input signal is a differential input signal, wherein the feedback capacitor includes first and second feedback capacitors and wherein the input capacitor includes first and second input capacitors, and wherein the node includes a first node between the first input capacitor and a first input of the mixer amplifier and a second node between the second input capacitor and a second input of the mixer amplifier, wherein the feedback path includes a first feedback path branch coupled to the first node via the first feedback capacitor and a second feedback path branch coupled to the second node via the second feedback capacitor, and wherein the second modulator includes a modulator in the first feedback path branch and a modulator in the second feedback path branch that modulate the amplitude of the output signal out of phase with one another. 14. The device of claim 12, wherein a gain of the mixer amplifier is at least partially dependent on a ratio of a capacitance value of the feedback capacitor to a capacitance value of the input capacitor. 15. The device of claim 12, wherein the feedback path is a first feedback path and the feedback capacitor is a first feedback capacitor, the device further comprising: an integrator that integrates the output signal; a third modulator that modulates the integrated output signal at the clock frequency to produce a second feedback signal; and a second feedback path that applies the second feedback signal to the modulated signal at the node between the input capacitor and the mixer amplifier via a second feedback capacitor. 16. The device of claim 15, wherein the mixer amplifier is a differential input mixer amplifier, the input signal is a differential input signal, the second feedback path includes a first feedback path branch coupled to a first input of the mixer amplifier and a second feedback path branch coupled to a second input of the mixer amplifier, and wherein the third modulator includes a modulator in the first feedback path branch and a modulator in the second feedback path branch that modulate the amplitude of the integrated output signal out of phase with one another. 17. The device of claim 16, wherein each of the first and second feedback path branches of the second feedback path includes a feedback path branch capacitor, and wherein the second feedback path is dominant at frequencies lower than a high pass cutoff frequency, and the first feedback path is dominant at frequencies above the high pass cutoff frequency. 18. The device of claim 12, wherein the mixer amplifier is a differential input mixer amplifier, and the input signal is a differential input signal, wherein the feedback capacitor includes first and second feedback capacitors and wherein the input capacitor includes first and second input capacitors, and wherein the node includes a first node between the first input capacitor and a first input of the mixer amplifier and a second node between the second input capacitor and a second input of the mixer amplifier, the amplifier further comprising a second feedback path including a first feedback path branch that couples an output of the mixer amplifier to a first input of the first modulator via a first switched capacitor, and a second feedback path branch that couples the output of the mixer amplifier to a second input of the first modulator via a second switched capacitor. 19. The device of claim 18, wherein each of the first and second switched capacitors is configured to apply a scaled compensatory charge to a respective one of the input capacitors. 20. The device of claim 12, further comprising a power source to power the amplifier, wherein the power source delivers less than approximately 2.0 microamps of electrical current to the amplifier during operation, and delivers a voltage of less than approximately 2.0 volts to the circuit. 21. The device of claim 12, wherein the input signal has a frequency of less than or equal to approximately 1.0 Hz. 22. The device of claim 12, wherein the sensor includes one of an accelerometer, a pressure sensor, and a voltage sensor. 23. The device of claim 22, wherein sensor includes one of an electrocardiogram (ECG), electromyogram (EMG), or electroencephalogram (EEG) sensor. 24. The device of claim 12, wherein the physiological sensing device resides within an implantable medical device. 25. The device of claim 24, wherein the implantable medical device includes one of a cardiac pacemaker, a cardiac defibrillator, an electrical neurostimulator, and an implantable drug delivery device. 26. The device of claim 12, wherein the mixer amplifier comprises an integrator that integrates the demodulated signal to produce the output signal. 27. A chopper-stabilized instrumentation amplifier comprising: means for modulating an amplitude of an input signal at a clock frequency to produce a modulated signal; means for amplifying the modulated signal to produce an amplified signal and demodulating the amplified signal at the clock frequency to produce an output signal; an input capacitor that couples the modulated signal to an input of the amplifying means; means for modulating an amplitude of the output signal at the clock frequency to produce a modulated output signal; and means for applying the modulated output signal as a feedback signal to the modulated input signal at a node between the input capacitor and an input of the amplifying means via a feedback capacitor. 28. A method comprising: modulating an amplitude of an input signal at a clock frequency to produce a modulated signal; amplifying the modulated signal in a mixer amplifier to produce an amplified signal, wherein an input capacitor couples the modulated signal to an input of the mixer amplifier; demodulating the amplified signal in the mixer amplifier at the clock frequency to produce an output signal; modulating an amplitude of the output signal at the clock frequency to produce a modulated output signal; and applying the modulated output signal as a feedback signal to the modulated signal via a first feedback path at a node between the input capacitor and the input of the mixer amplifier via a feedback capacitor. 29. The method of claim 28, wherein the mixer amplifier is a differential input mixer amplifier, and the input signal is a differential input signal, wherein the feedback capacitor includes first and second feedback capacitors and wherein the input capacitor includes first and second input capacitors, and wherein the node includes a first node between the first input capacitor and a first input of the mixer amplifier and a second node between the second input capacitor and a second input of the mixer amplifier, further comprising applying the feedback signal via a first feedback path branch, of the first feedback path, coupled to the first node via the first feedback capacitor and a second feedback path branch, of the first feedback path, coupled to the second node via the second feedback capacitor, wherein modulating an amplitude of the output signal comprises modulating the amplitude of the output signal in the first feedback path branch and modulating the amplitude of the output signal in the second feedback path branch out of phase with modulation in the first feedback path branch. 30. The method of claim 28, wherein a gain of the mixer amplifier is at least partially dependent on a ratio of a capacitance value of the feedback capacitor to a capacitance value of the input capacitor. 31. The method of claim 28, wherein the feedback path is a first feedback path and the feedback capacitor is a first feedback capacitor, the method further comprising: integrating the output signal; modulating the integrated output signal at the clock frequency to produce a second differential feedback signal; and applying the second feedback signal to the modulated signal at the node between the input capacitor and the input of the mixer amplifier via a second feedback capacitor via a second feedback path. 32. The method of claim 31, wherein the mixer amplifier is a differential input mixer amplifier, and the input signal is a differential input signal, the second feedback path includes a first feedback path branch, of the second feedback path, coupled to a first input of the mixer amplifier and a second feedback path branch, of the second feedback path, coupled to a second input of the mixer amplifier, and modulating the integrated output signal comprises modulating the amplitude of the integrated output signal in the first feedback path branch and modulating the amplitude of the integrated output signal in the second feedback path branch out of phase with modulation in the first feedback path branch. 33. The method of claim 32, wherein each of the first and second feedback path branches of the second feedback path includes a feedback path branch capacitor, and wherein the second feedback path is dominant at frequencies lower than a high pass cutoff frequency, and the first feedback path is dominant at frequencies above the high pass cutoff frequency. 34. The method of claim 28, wherein the mixer amplifier is a differential input mixer amplifier, and the input signal is a differential input signal, wherein the feedback capacitor includes first and second feedback capacitors and wherein the input capacitor includes first and second input capacitors, and wherein the node includes a first node between the first input capacitor and a first input of the mixer amplifier and a second node between the second input capacitor and a second input of the mixer amplifier, the method further comprising applying feedback from an output of the mixer amplifier to a first input of the first modulator via a first switched capacitor, and applying feedback from the output of the mixer amplifier to a second input of the first modulator via a second switched capacitor. 35. The method of claim 34, further comprising applying a scaled compensatory charge to each of the input capacitors via the respective first and second switched capacitors. 36. The method of claim 28, further comprising powering the mixer amplifier with less than approximately 2.0 microamps of electrical current and less than approximately 2.0 volts of electrical voltage during operation. 37. The method of claim 28, wherein the input signal has a frequency of less than or equal to approximately 1.0 Hz. 38. The method of claim 28, further comprising integrating the demodulated signal in an integrator of the mixer amplifier to produce the output signal. 39. A chopper-stabilized instrumentation amplifier comprising: a first modulator that modulates an amplitude of an input signal at a clock frequency to produce a modulated signal; a mixer amplifier that amplifies the modulated signal to produce an amplified signal and demodulates the amplified signal at the clock frequency to produce an output signal; a second modulator that modulates an amplitude of the output signal at the clock frequency; a first feedback path that applies the modulated output signal as a feedback signal to the modulated input signal; an integrator that integrates the output signal; a third modulator that modulates the integrated output signal at the clock frequency to produce a second feedback signal; and a second feedback path that applies the second feedback signal to the modulated input signal. 40. The amplifier of claim 39, wherein the mixer amplifier is a differential input mixer amplifier, and the input signal is a differential input signal, wherein the first feedback path includes a first feedback path branch coupled to a first input of the mixer amplifier via a first feedback capacitor and a second feedback path branch coupled to a second input of the mixer amplifier via a second feedback capacitor, and wherein the second feedback path includes a third feedback path branch coupled to the first input of the mixer amplifier via a third feedback capacitor and a fourth feedback path branch coupled to the second input of the mixer amplifier via a fourth feedback capacitor, and wherein the third modulator includes a modulator in the third feedback path branch and a modulator in the fourth feedback path branch that modulate the amplitude of the integrated output signal out of phase with one another, and wherein the second feedback path is dominant at frequencies lower than a high pass cutoff frequency, and the first feedback path is dominant at frequencies above the high pass cutoff frequency. 41. A chopper-stabilized instrumentation amplifier comprising: a first modulator that modulates an amplitude of an input signal at a clock frequency to produce a modulated signal; a mixer amplifier that amplifies the modulated signal to produce an amplified signal and demodulates the amplified signal at the clock frequency to produce an output signal; a second modulator that modulates an amplitude of the output signal at the clock frequency; and a first feedback path that applies the modulated output signal as a feedback signal to the modulated input signal; a second feedback path that applies the output signal to the input signal via a switched capacitor. 42. The amplifier of claim 41, wherein the mixer amplifier is a differential input mixer amplifier having first and second inputs, the input signal is a differential input signal, the first input of the mixer amplifier is coupled to a first output of the first modulator via a first input capacitor, the second input of the mixer amplifier being coupled to a second output of the first modulator via a second input capacitor, the switched capacitor includes first and second switched capacitors, the second feedback path includes a first feedback path branch that couples an output of the mixer amplifier to a first input of the first modulator via the first switched capacitor, and a second feedback path branch that couples the output of the mixer amplifier to a second input of the first modulator via the second switched capacitor. 43. The amplifier of claim 42, wherein each of the first and second switched capacitors is configured to apply a scaled compensatory charge to a respective one of the input capacitors. 44. A method comprising: modulating an amplitude of a input signal at a clock frequency to produce a modulated signal; amplifying the modulated signal in a mixer amplifier to produce an amplified signal; demodulating the amplified signal in the mixer amplifier at the clock frequency to produce an output signal; modulating an amplitude of the output signal at the clock frequency; applying the modulated output signal as a feedback signal to the modulated input signal via a first feedback path; integrating the output signal; modulating the integrated output signal at the clock frequency to produce a second feedback signal; and applying the second feedback signal to the modulated input signal via a second feedback path. 45. The method of claim 44, wherein the mixer amplifier is a differential input mixer amplifier, and the input signal is a differential input signal, wherein the first feedback path includes a first feedback path branch coupled to a first input of the mixer amplifier via a first feedback capacitor and a second feedback path branch coupled to a second input of the mixer amplifier via a second feedback capacitor, and wherein the second feedback path includes a third feedback path branch coupled to the first input of the mixer amplifier via a third feedback capacitor and a fourth feedback path branch coupled to the second input of the mixer amplifier via a fourth feedback capacitor, wherein modulating the integrated output Signal comprises modulating an amplitude of the integrated output signal in the first feedback path branch and modulating the amplitude of the integrated output signal in the second feedback path branch out of phase with modulation in the first feedback path branch, and wherein the second feedback path is dominant at frequencies lower than a high pass cutoff frequency, and the first feedback path is dominant at frequencies above the high pass cutoff frequency. 46. A method comprising: modulating an amplitude of a input signal at a clock frequency to produce a modulated signal; amplifying the modulated signal in a mixer amplifier to produce an amplified signal; demodulating the amplified signal in the mixer amplifier at the clock frequency to produce an output signal; modulating an amplitude of the output signal at the clock frequency; applying the modulated output signal as a feedback signal to the modulated input signal via a first feedback path; and applying the output signal to the input signal via a switched capacitor. 47. The method of claim 46, wherein the mixer amplifier is a differential input mixer amplifier having first and second inputs, the input signal is a differential input signal, the first input of the mixer amplifier is coupled to a first output of the first modulator via a first input capacitor, the second input of the mixer amplifier being coupled to a second output of the first modulator via a second input capacitor, the switched capacitor includes first and second switched capacitors, the second feedback path includes a first feedback path branch that couples an output of the mixer amplifier to a first input of the first modulator via the first switched capacitor, and a second feedback path branch that couples the output of the mixer amplifier to a second input of the first modulator via the second switched capacitor. 48. The amplifier of claim 47, wherein each of the first and second switched capacitors is configured to apply a scaled compensatory charge to a respective one of the input capacitors. 49. The amplifier of claim 1, wherein the mixer amplifier includes a differential mixer amplifier, the input signal comprises a differential input signal, and the feedback signal comprises a differential feedback signal. 50. The device of claim 12, wherein the mixer amplifier includes a differential mixer amplifier, the input signal comprises a differential input signal, and the feedback signal comprises a differential feedback signal. 51. The device of claim 27, wherein the amplifying means includes a differential mixer amplifier, the input signal comprises a differential input signal, and the feedback signal comprises a differential feedback signal. 52. The device of claim 28, wherein the mixer amplifier includes a differential mixer amplifier, the input signal comprises a differential input signal, and the feedback signal comprises a differential feedback signal. 53. A chopper-stabilized instrumentation amplifier comprising: a first modulator that modulates an amplitude of a differential input signal to produce a modulated signal; a differential mixer amplifier that amplifies the modulated signal to produce an amplified signal and demodulates the amplified signal at the clock frequency to produce an output signal; a first input capacitor coupled between a first output of the first modulator and a first input of the mixer amplifier; a second input capacitor coupled between a second output of the first modulator and a second input of the mixer amplifier; a first feedback branch comprising a first modulator that modulates the output signal to produce a first modulated output signal, wherein the first feedback branch couples the first modulated output signal to a first node between the first input capacitor and the first input of the mixer amplifier via a first feedback capacitor; and a second feedback branch comprising a second modulator that modulates the output signal to produce a second modulated output signal out of phase with the first modulated output signal, wherein the second feedback branch couples the second modulated output signal to a second node between the second input capacitor and the second input of the mixer amplifier via a second feedback capacitor. 54. The amplifier of claim 53, wherein a gain of the mixer amplifier is at least partially dependent on a ratio of a capacitance value of the first feedback capacitor to a capacitance value of the first input capacitor and a ratio of a capacitance value of the second feedback capacitor to a capacitance value of the second input capacitor.