Chopper-stabilized instrumentation amplifier
First Claim
1. An electrical circuit comprising:
- a first modulator configured to modulate an amplitude of an input signal at a selected frequency to produce a modulated signal;
an amplifier configured to amplify the modulated signal to produce an amplified signal;
a first demodulator configured to demodulate the amplified signal at the selected frequency to produce an output signal;
an input capacitor coupled between an output of the first modulator and an input of the amplifier;
a second modulator configured to modulate an amplitude of the output signal at the selected frequency to produce a modulated output signal; and
a feedback path coupled between an output of the second modulator and a node between the input capacitor and the input of the amplifier, wherein the feedback path includes a feedback capacitor.
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Abstract
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.
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Citations
34 Claims
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1. An electrical circuit comprising:
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a first modulator configured to modulate an amplitude of an input signal at a selected frequency to produce a modulated signal; an amplifier configured to amplify the modulated signal to produce an amplified signal; a first demodulator configured to demodulate the amplified signal at the selected frequency to produce an output signal; an input capacitor coupled between an output of the first modulator and an input of the amplifier; a second modulator configured to modulate an amplitude of the output signal at the selected frequency to produce a modulated output signal; and a feedback path coupled between an output of the second modulator and a node between the input capacitor and the input of the amplifier, wherein the feedback path includes a feedback capacitor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method comprising:
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modulating an amplitude of an input signal at a selected frequency to produce a modulated input signal; amplifying the modulated input signal with an amplifier to produce an amplified signal, wherein an input capacitor couples the modulated input signal to an input of the amplifier; demodulating the amplified signal at the selected frequency to produce an output signal; modulating an amplitude of the output signal at the selected frequency to produce a modulated output signal; and applying the modulated output signal to the modulated input signal via a feedback path at a node between the input capacitor and the input of the amplifier via a feedback capacitor. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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20. An implantable medical device comprising:
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a physiological sensor that senses a physiological signal as an input signal; a first modulator configured to modulate an amplitude of the input signal at a selected frequency to produce a modulated signal; an amplifier configured to amplify the modulated signal to produce an amplified signal; a first demodulator configured to demodulate the amplified signal at the selected frequency to produce an output signal; an input capacitor coupled between an output of the first modulator and an input of the amplifier; a second modulator configured to modulate an amplitude of the output signal at the selected frequency to produce a modulated output signal; and a feedback path coupled between an output of the second modulator and a node between the input capacitor and the input of the amplifier, wherein the feedback path includes a feedback capacitor. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28)
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29. An implantable medical device comprising:
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means for sensing a physiological signal as an input signal; means for modulating an amplitude of the input signal at a selected frequency to produce a modulated input signal; means for amplifying the modulated input signal with an amplifier to produce an amplified signal, wherein an input capacitor couples the modulated input signal to an input of the amplifying means; means for demodulating the amplified signal at the selected frequency to produce an output signal; means for modulating an amplitude of the output signal at the selected frequency to produce a modulated output signal; and means for applying the modulated output signal to the modulated input signal via a first feedback path at a node between the input capacitor and the input of the amplifying means via a feedback capacitor. - View Dependent Claims (30, 31, 32, 33, 34)
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Specification