公开(公告)号：US20180020288A1

公开(公告)日：2018-01-18

申请号：US15395290

申请日：2016-12-30

Applicant: TEXAS INSTRUMENTS INCORPORATED

Inventor： Lars RISBO ,  Ryan Erik LIND ,  Jasjot Singh CHADHA

IPC: H04R3/02 ,  H03F3/185 ,  H03F3/217

CPC classification number: H04R3/02 ,  H03F3/185 ,  H03F3/2173 ,  H03F3/3022 ,  H03F3/45192 ,  H03F2200/03 ,  H03F2200/351 ,  H03F2200/411 ,  H04R3/00

Abstract: A system includes a class D amplifier and a current steering digital-to-analog converter (DAC) directly connected to the class D amplifier. The system also includes a common mode servo circuit coupled to a node interconnecting the current steering DAC to the class D amplifier. The common servo circuit amplifies a difference between a common mode signal determined from the node and a reference voltage and generates a feedback current to the node based on the amplified difference. A feed-forward common-mode compensation circuit is included to reduce an alternating current (AC) ripple from the class D amplifier. The feed-forward common-mode compensation circuit includes first and second resistors coupled to respective outputs of the class D amplifier. A current mirror is coupled to the first and second resistors and is configured to sink a current from the node to ground that approximates a common mode feedback current of the class D amplifier.