Amplifier common-mode control methods
AssigneeDialog Semiconductor GmbH
InventorAndrew Myles
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Abstract
Systems and methods for providing a fully differential amplifier performing common-mode voltage control having reduced area and power requirements are disclosed. The amplifier disclosed comprises an additional input stage at the amplifier input which senses the common mode voltage of the amplifier's inputs and applies internal feedback control to adjust the output common-mode voltage until the input common-mode voltage matches a target voltage and thereby indirectly set the output common-mode voltage. Furthermore the internal common-mode control can be implemented in such a manner as to provide a feed-forward transconductance function in addition to common-mode control if desired. Moreover it is possible to use feedback from other amplifier stages in an amplifier chain to implement common-mode feedback.
Claims20
A method to achieve a fully differential amplifier performing common-mode voltage control having reduced area and power requirements, comprising the following steps:
- (1) providing a fully differential amplifier having a continuous-time signal path feedback network between amplifier's differential inputs and differential outputs;
- and
- (2) deploying an additional input stage at the amplifier's input, which senses the common-mode voltage of the amplifier's input, compares the input common-mode voltage with a reference voltage, and regulates, depending on the result of the comparison, the output common-mode voltage via the existing continuous signal path feedback network without requiring devices additional to the existing signal path network, wherein the common-mode voltage control is implemented in such a manner as to provide a feed-forward transconductance function in addition to the common-mode control.
A fully differential amplifier having a continuous-time signal path feedback network wherein a differential common-mode outputs voltage Vcmo is controlled indirectly by controlling a differential inputs common-mode voltage Vcm and wherein Vcmo is controlled via Vcm without requiring devices additional to the signal path feedback network to sense Vcmo directly wherein Vcm is easily sensed by an additional differential stage at the amplifier input and wherein the common-mode voltage control is implemented in such a manner as to provide a feed-forward transconductance function in addition to the common-mode control.
Dependencies are inferred from the claim text.