Preamplifier with improved CMRR and temperature stability and associated amplification method
AssigneeTexas Instruments Incorporated
InventorAlfio Zanchi
Life of this patent
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Abstract
A preamplifier that is substantially resilient to temperature and input common-mode variations includes a feedback network coupled to regulate a common mode voltage of the preamplifier. The preamplifier can be implemented as a first stage of a multi-stage op amp, which provides an intermediate output to a next stage of the op amp. The feedback and associated temperature stability can be facilitated by downshifting the output voltage of the preamplifier and increasing the output impedance of the preamplifier.
Claims30
A preamplifier system for a differential operational amplifier, comprising:
- at least two input devices coupled to receive respective parts of a differential input signal, each of the input devices being coupled to bias an associated output of the preamplifier system;
- a pair of gain resistors coupled in series between the outputs of the preamplifier system, a juncture between the resistors defining a common mode node;
- and
- a feedback network coupled to regulate a common mode voltage at the common mode node, whereby the preamplifier system is substantially resilient to temperature and input common mode variations.
A multi-stage operational amplifier, comprising:
- a first stage that includes at least one input device coupled to receive an input signal and provide an intermediate differential output signal functionally related to the input signal;
- a feedback network coupled to a common mode node of the first stage to regulate a common mode voltage at the common mode node, such that the preamplifier system is substantially resilient to temperature variations;
- and
- a second stage coupled to amplify the intermediate output signal of the first stage and to provide an associated output signal as a function thereof according to a gain of the second stage.
A multi-stage operational amplifier, comprising:
- first means for amplifying an input signal to provide an intermediate output signal according to a first gain, the first means for amplifying having a common mode voltage;
- means for increasing an output impedance of the first means for amplifying;
- feedback means for regulating the common mode voltage of the first means for amplifying;
- and
- second means for amplifying the intermediate output signal to provide an output signal according to a second gain, which is greater than the first gain.
A method for amplifying an input signal to provide an intermediate signal for a next stage of a multi-stage amplifier, the method comprising:
- increasing an associated output impedance of a first stage;
- and
- regulating a common mode voltage of the first stage such that the intermediate signal provided by the first stage is substantially resistant to temperature variations.
Dependencies are inferred from the claim text.