Differential amplifier with a common mode voltage loop
AssigneeSTMicroelectronics S.r.l.
InventorFrançois Van Zanten
Life of this patent
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Abstract
An amplifier circuit comprising an amplification chain having a differential output stage; a common mode correction block acting on the input of the output stage as a function of a common mode voltage at the output of said stage and introducing a phase shift between its input and its output for frequencies close to the cut-off frequency of the circuit; and, in parallel with the correction block, a means introducing no phase shift between its input and its output and having at frequencies greater than or equal to the circuit cut-off frequency an output impedance much smaller than the output impedance of the correction block.
Claims26
An amplifier circuit comprising:
- an amplification chain having at least an input stage and a differential output stage;
- a common mode correction block acting on the input of the output stage as a function of a common mode voltage at the output of said stage and introducing a phase shift between its input and its output for frequencies close to the cut-off frequency of the circuit;
- and
- in parallel with the correction block, a means introducing no phase shift between its input and its output and having at frequencies close to the circuit cut-off frequency an output impedance much smaller than the output impedance of the correction block.
A common mode correction circuit operable in a normal mode to develop a common mode feedback value on an output in response to an input signal applied on an input, and operable in a cut-off mode when the input signal is near a cut-off frequency to inhibit the development of the common mode feedback value on the output.
An amplifier circuit, comprising:
- a first differential amplifier having at least one input and differential outputs;
- a common mode correction circuit having inputs coupled to the outputs of the first differential amplifier and having an output coupled to the input of the first differential amplifier, the common mode correction circuit operable in a normal mode to develop a common mode feedback value on its output in response to signals applied on its inputs, and operable in a cut-off mode when the input signals are near a cut-off frequency to inhibit the development of the common mode feedback value on the output.
An electronic system, comprising:
- electronic circuitry including an amplifier circuit, including,
- a first differential amplifier having at least one input and differential outputs;
- a common mode correction circuit having inputs coupled to the outputs of the first differential amplifier and having an output coupled to the input of the first differential amplifier, the common mode correction circuit operable in a normal mode to develop a common mode feedback value on its output in response to signals applied on its inputs, and operable in a cut-off mode when the input signals are near a cut-off frequency to inhibit the development of the common mode feedback value on the output.
A method of controlling a common mode feedback value in an amplifier having at least one input and differential outputs, the method comprising:
- developing a feedback value responsive to signals on the outputs of the amplifier when the frequency of an input signal applied to the differential amplifier is not near a cut-off frequency;
- applying the feedback value to the input of the differential amplifier;
- and
- disabling application of the feedback value to the input of the amplifier when the frequency of the input signal is near the cut-off frequency.
Dependencies are inferred from the claim text.