Abstract: A system has a current mirror that has an input node and an output node and an avalanche photodiode (APD) coupled to the output node of the current mirror. The system also has a nonlinear voltage-to-current conversion element coupled to the input node of the current mirror that transmits current through the current mirror and the APD. Further, the system has a feedback path coupled between the output node of the current mirror and the voltage-to-current conversion element that senses a voltage across the APD and provides, based on the sensed voltage, an input signal to the voltage-to-current conversion element for controlling the element's output current, and the feedback path is arranged to limit a voltage of the input signal such that the output current is limited thereby preventing damage to the APD.

Abstract: A device for echo attenuation in a digital transmission system comprises an impedance replica of the transmission path. The impedance replica consists of a terminating resistance replica, a transformer replica, and a transmission line replica. The device may further comprise a bridged tap replica. The transformer replica and the bridged tap replica are provided as on-chip components. The main transformer inductance replica and all components of the bridged tap replica are variable and may be set by software control.