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; and
a low pass filter configured to provide band limiting of the output 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; and
wherein, within each of the multi-path amplifiers, the differential input transconductance stage of the high frequency path is noisier than, but consumes less power than, the differential input transconductance stage of the low frequency path.
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Accused Products
Abstract
An 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 input signals. A low pass filter provides passive band limiting of the output signal. Each operational amplifier is 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. Further, each multi-path amplifier includes a differential input transconductance stage within the low frequency path and a differential input transconductance stage within the high frequency path. Within each multi-path amplifier, the differential input transconductance stage of the high frequency path is noisier than, but consumes less power than, the differential input transconductance stage of the low frequency path. Each multi-path amplifier provides noise shaping that results in an increase in noise above a crossover frequency of the multi-path amplifier.
10 Citations
23 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; and a low pass filter configured to provide band limiting of the output 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; and wherein, within each of the multi-path amplifiers, the differential input transconductance stage of the high frequency path is noisier than, but consumes less power than, the differential input transconductance stage of the low frequency path. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for use with 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, the method comprising:
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(a) performing noise shaping within each of the operational amplifiers of the instrumentation amplifier, which results in an increase in noise above a crossover frequency; and (b) performing passive band limiting of the output signal to thereby filter out noise above a cutoff frequency. - View Dependent Claims (12, 13, 14, 15, 16)
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17. 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; and a 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; 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; and wherein Gmf=Gms/N and Ccs=Ccf/N, where N>
1. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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Specification