Notch filter for ripple reduction in chopper stabilized amplifiers
First Claim
1. A chopper-stabilized amplifier comprising:
- (a) a first operational transconductance amplifier;
(b) first chopper circuitry coupled to an input of the first operational transconductance amplifier for chopping an input signal and applying the chopped input signal to the input of the first operational transconductance amplifier, and second chopper circuitry coupled to an output of the first operational transconductance amplifier for chopping an output signal produced by the first operational transconductance amplifier; and
(c) a switched capacitor notch filter having an input coupled to an output of the second chopper circuitry and performing an integrate and transfer function on a chopped output signal produced by the second chopper circuitry to filter a chopped output signal produced by the second chopper circuitry by operating synchronously with a chopping frequency of the second chopper circuitry to notch filter ripple voltages that otherwise would occur in the output of the second chopper circuitry.
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Reexamination
Accused Products
Abstract
A chopper-stabilized amplifier receiving an input signal includes a first operational transconductance amplifier having an input chopper and an output chopper for chopping an output signal produced by the first operational transconductance amplifier. A switched capacitor notch filter filters the chopped output signal by operating synchronously with the chopping frequency of output chopper to filter ripple voltages that otherwise would be produced by the output chopper. In one embodiment, a second operational transconductance amplifier amplifies the notch filter output. The input signal is fed forward, summed with the output of the second operational transconductance amplifier, and applied to the input of a fourth operational transconductance amplifier. Ripple noise and offset are substantially reduced.
140 Citations
20 Claims
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1. A chopper-stabilized amplifier comprising:
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(a) a first operational transconductance amplifier; (b) first chopper circuitry coupled to an input of the first operational transconductance amplifier for chopping an input signal and applying the chopped input signal to the input of the first operational transconductance amplifier, and second chopper circuitry coupled to an output of the first operational transconductance amplifier for chopping an output signal produced by the first operational transconductance amplifier; and (c) a switched capacitor notch filter having an input coupled to an output of the second chopper circuitry and performing an integrate and transfer function on a chopped output signal produced by the second chopper circuitry to filter a chopped output signal produced by the second chopper circuitry by operating synchronously with a chopping frequency of the second chopper circuitry to notch filter ripple voltages that otherwise would occur in the output of the second chopper circuitry. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method of operating a chopper-stabilized amplifier including a first operational transconductance amplifier, the method comprising:
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(a) chopping an input signal and applying the chopped input signal to the input of the first operational transconductance amplifier, and chopping an output signal produced by the first operational transconductance amplifier at a chopping frequency to produce a chopped output signal; and (b) operating a switched capacitor notch filter having an input coupled to receive the chopped output signal by performing an integrate and transfer function on a chopped output signal produced by the second chopper circuitry synchronously with the chopping frequency to notch filter ripple voltages that otherwise would occur in the chopped output signal. - View Dependent Claims (18, 19)
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20. A chopper-stabilized amplifier comprising:
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(a) a first operational transconductance amplifier; (b) first chopper circuitry coupled to an input of the first operational transconductance amplifier for chopping an input signal and applying the chopped input signal to the input of the first operational transconductance amplifier, and second chopper circuitry coupled to an output of the first operational transconductance amplifier for chopping an output signal produced by the first operational transconductance amplifier; and (c) switched capacitor notch filter means having an input coupled to receive the chopped output signal for performing an integrate and transfer function on a chopped output signal produced by the second chopper circuitry synchronously with the chopping frequency to notch filter ripple voltages that otherwise would occur in the chopped output signal.
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Specification