Amplifier system with current-mode servo feedback
First Claim
1. An amplifier apparatus comprising:
- differential inputs disposed to receive a first and second input signal;
a primary differential amplifier having inverting and non-inverting input nodes receiving said first and second input signal through respective first and second impedance elements and providing a main output signal; and
feedback circuitry disposed to sample said main output signal and convey complementary current-mode negative feedback signals to said inverting and non-inverting input nodes.
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Abstract
A system and method for compensating an amplifier apparatus for low frequency and/or DC components of an externally applied input signal as well as for any voltage offsets contributed by the amplifier circuitry. Band-limited servo feedback is applied to predetermined nodes in the forward gain path to null out unwanted signal components, leaving a residual signal that, when amplified, will be centered around ground, so that the full dynamic range of the amplifier system may be utilized. Consequently, the signal-to-noise ratio available at the output of the amplifier system will be maximized. The servo compensation may either operate in continuous time, or it may be held constant once a suitable level of compensation has been established, or it may be adjusted from time to time to accommodate slow variations of the average DC component of the input signal.
154 Citations
41 Claims
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1. An amplifier apparatus comprising:
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differential inputs disposed to receive a first and second input signal; a primary differential amplifier having inverting and non-inverting input nodes receiving said first and second input signal through respective first and second impedance elements and providing a main output signal; and feedback circuitry disposed to sample said main output signal and convey complementary current-mode negative feedback signals to said inverting and non-inverting input nodes. - View Dependent Claims (17)
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2. An amplifier apparatus comprising:
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differential inputs disposed to receive a first and second input signal; a primary differential amplifier having inverting and non-inverting input nodes receiving said first and second input signal through respective first and second impedance elements and providing a main output signal; and feedback circuitry disposed to sample said main output signal and convey complementary current-mode negative feedback signals to said inverting and non-inverting input nodes, wherein said current-mode feedback signals are each servo feedback signals having the same low-pass characteristic. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 31, 32, 33, 34)
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10. An amplifier apparatus comprising:
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a first input differential amplifier disposed to receive a first input signal at its non-inverting input and output a first intermediate output signal; a second input differential amplifier disposed to receive a second input signal at its non-inverting input and output a second intermediate output signal; a primary differential amplifier disposed to receive at its non-inverting input said first intermediate output signal conveyed through a first impedance element and to receive at its inverting input said second intermediate output signal conveyed through a second impedance element, and provide a main output signal at its output node; and feedback circuitry disposed to sample said main output signal and convey a first negative feedback signal to said inverting input of said first input differential amplifier, and a second negative feedback signal to said inverting input of said second input differential amplifier. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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30. A signal detection and amplification system comprising amplifier apparatus having:
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differential inputs disposed to receive a first and second input signal; a primary differential amplifier receiving said first and second input signal and providing a main output signal; and feedback circuitry disposed to sample said main output signal and convey complementary current-mode negative feedback signals to said differential inputs.
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35. A method for compensating an output of an amplifier system comprising:
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integrating said output to generate a feedback control signal; controlling a pair of complementary current mode feedback signals with said feedback control signal; connecting said pair of complementary current mode feedback signals to input nodes of a primary amplifier wherein said input nodes are connected through impedance elements to differential inputs of said amplifier system. - View Dependent Claims (36, 37, 38, 39)
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40. An amplifier apparatus comprising:
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a primary amplifier providing a main output signal; and feedback means disposed to sample said main output signal and convey complementary current-mode negative feedback signals to said primary amplifier.
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41. An amplifier apparatus comprising:
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a primary amplifier providing a main output signal; and feedback means disposed to sample said main output signal and convey complementary current-mode negative feedback signals to said primary amplifier, wherein a DC value of said main output signal is substantially equal to a reference potential.
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Specification