Abstract: A reference buffer circuit includes a first switched capacitor selectively coupled to a first node that receives a reference voltage from a buffer device connected to the first node. A second switched capacitor is selectively coupled to a voltage source to receive a charging voltage from the voltage source. A first switch is coupled to the first switched capacitor to switch communication of the first switched capacitor between the first node and a second node. And, a second switch is coupled to the second switched capacitor to switch communication of the second switched capacitor between the voltage source and the first node, wherein the second switched capacitor delivers the charging voltage to the first switched capacitor.

Abstract: According to one aspect of the invention, an apparatus is provided which includes a first amplifier and a common mode feedback circuit. The first amplifier includes a first input, a second input, a first output, and a second output. The first input and the second input are coupled to receive a first input voltage and a second input voltage, respectively. The first and second outputs provide a first output voltage and a second output voltage, respectively. The common mode feedback circuit has first and second switched capacitors coupled to provide a common mode feedback signal based on the first and second output voltages to the first and second inputs of first amplifier.

Abstract: A system and method for echo cancellation in digital subscriber line (DSL) service using passive devices. The outgoing transmitted signal is attenuated and fed back into the receiver circuit in such a way as to maximize the canceling of the transmitted signal and thus allow the receiver circuit to amplify and process the received signal without interference from the outgoing transmitted signal. The feedback circuit uses only passive elements. The feedback circuit has complex impedance branches. These complex impedance branches parallel the complex impedances of the transformer and transmission line such that any change in the transformer or transmission line impedance is similarly experienced in the feedback circuit. This allows for near total cancellation of the echo signal without the need for costly active circuits.

Abstract: A line driver with an integrated termination comprises a driver current mirror, a feedback resistor, and a controlled current buffer. The feedback resistor and controlled current buffer may be coupled between the output and the input of the driver current mirror. The controlled current buffer may respond to the static current flowing through the feedback resistor. In an embodiment, the controlled current buffer output a static current that is reduced compared to other line drivers.