DYNAMICALLY ADJUSTABLE LOW NOISE, LOW POWER INSTRUMENTATION AMPLIFIER
First Claim
1. A circuit, comprising:
- an instrumentation amplifier including a pair of buffered operational amplifiers that accept a pair of input signals, and a differential operational amplifier that outputs an output signal indicative of a difference between the pair of input signals;
a dynamically adjustable low pass filter configured to provide band limiting of the output signal at frequencies greater than a cutoff frequency;
at least one monitor configured to monitor a signal upstream of the instrumentation amplifier and/or a signal downstream of the instrumentation amplifier and output a monitor signal;
wherein each of the buffered operational amplifiers and the differential operational amplifier are implemented as a multi-path amplifier that includes a low frequency path and a high frequency path between an input and an output of the operational amplifier;
wherein each of the multi-path amplifiers includes a differential input transconductance stage within the low frequency path and a differential input transconductance stage within the high frequency path;
wherein, within each of the multi-path amplifiers, the differential input transconductance stage of the high frequency path is configured to provide dynamically adjustable noise shaping by producing more noise but consuming less power than the differential input transconductance stage of the low frequency path above a crossover frequency; and
a controller configured to receive at least one of said monitor signal, wherein the controller is configured to dynamically adjust output voltage noise at frequencies greater than the crossover frequency of the multipath amplifiers and/or the cutoff frequency of the low pass filter based on at least one said monitor signal.
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Accused Products
Abstract
A circuit in accordance with an embodiment of the present invention includes an instrumentation amplifier, a dynamically adjustable low pass filter, at least one monitor and a controller. The instrumentation amplifier includes a pair of buffered operational amplifiers that accept a pair of input signals, and a differential operational amplifier that outputs an output signal indicative of a difference between the pair of input signals. The dynamically adjustable low pass filter is configured to provide band limiting of the output signal at frequencies greater than a cutoff frequency. The monitor, or monitors, is/are configured to monitor a signal upstream of the instrumentation amplifier and/or a signal downstream of the instrumentation amplifier and output a monitor signal. The controller is configured to receive the monitor signal, or signals, and to dynamically adjust output voltage noise at frequencies greater than the crossover frequency of the multipath amplifiers and/or the cutoff frequency of the low pass filter based on the monitor signal, or signals.
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Citations
19 Claims
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1. A circuit, comprising:
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an instrumentation amplifier including a pair of buffered operational amplifiers that accept a pair of input signals, and a differential operational amplifier that outputs an output signal indicative of a difference between the pair of input signals; a dynamically adjustable low pass filter configured to provide band limiting of the output signal at frequencies greater than a cutoff frequency; at least one monitor configured to monitor a signal upstream of the instrumentation amplifier and/or a signal downstream of the instrumentation amplifier and output a monitor signal; wherein each of the buffered operational amplifiers and the differential operational amplifier are implemented as a multi-path amplifier that includes a low frequency path and a high frequency path between an input and an output of the operational amplifier; wherein each of the multi-path amplifiers includes a differential input transconductance stage within the low frequency path and a differential input transconductance stage within the high frequency path; wherein, within each of the multi-path amplifiers, the differential input transconductance stage of the high frequency path is configured to provide dynamically adjustable noise shaping by producing more noise but consuming less power than the differential input transconductance stage of the low frequency path above a crossover frequency; and a controller configured to receive at least one of said monitor signal, wherein the controller is configured to dynamically adjust output voltage noise at frequencies greater than the crossover frequency of the multipath amplifiers and/or the cutoff frequency of the low pass filter based on at least one said monitor signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for use with a dynamically adjustable instrumentation amplifier including a pair of buffered operational amplifiers that accept a pair of input signals, and a differential operational amplifier that outputs an output signal indicative of a difference between the pair of input signals, the method comprising:
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(a) monitoring a signal upstream of the dynamically adjustable instrumentation amplifier and/or a signal downstream of the dynamically adjustable instrumentation amplifier; and (b) dynamically adjusting noise shaping within each of the operational amplifiers of the instrumentation amplifier based on the monitoring to thereby increase output voltage noise at frequencies greater than a crossover frequency, and/or dynamically adjusting passive band limiting of the output signal based on the monitoring to thereby filter out output voltage noise at frequencies greater than a cutoff frequency. - View Dependent Claims (14, 15, 16, 17, 18)
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19. A circuit, comprising:
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a first operational amplifier configured as a buffer, and including an input that accepts a first input signal and including an output; a second operational amplifier configured as a buffer, and including an input that accepts a second input signal and including an output; a third operational amplifier configured as differential amplifier and including an inverting input, a non-inverting input, and an output; a first resistor connecting the output of the first operational amplifier to the inverting input of the third operational amplifier; a second resistor connecting the output of the second operational amplifier to the non-inverting input of the third operational amplifier; a dynamically adjustable low pass filter configured to band limit an output signal, indicative of a difference between the pair of input signals, provided at the output of the third operational amplifier; at least one monitor configured to monitor the first and second input signals and/or the output signal and output at least one monitor signal; a controller configured to receive the at least one monitor signal and dynamically adjust the dynamically adjustable low pass filter based on the at least one monitor signal; wherein each of the first, second and third operational amplifiers comprises a multi-path amplifier including a low frequency path and a high frequency path, with the low frequency path including an input transconductance stage (Gms) and the high frequency path including an input transconductance stage (Gmf), and with capacitors (Ccs and Ccf) that provide parallel integration paths for the low and high frequency paths; wherein Gmf/Ccf=Gms/Ccs; and wherein the controller is further configured to control noise shaping in each multi-path amplifier by dynamically adjusting Gmf and Ccf based on the monitor signal.
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Specification