Lucent Technologies Inc.

At+t Corp.

At&t Bell Laboratories

Haideh Khorramabadi

Maurice J Tarsia

Liang D Tzeng

Nam Sung Woo

The present invention provides an apparatus and method of tuning the frequency characteristics of a continuous-time filter. First and second test signals are provided to a filter means and the respective first and second responses of the filter means are measured. The first and second responses are compared and based on the comparison a tuning control signal is provided to the filter means to tune the frequency response characteristics of the filter means. During a tuning phase of operation, a first switch connects a test signal generator and disconnects a data signal generator from the transmission input of a continuous-time filter. A signal processor receives a signal from the transmission output from the continuous-time filter and produces a tuning control signal based on that signal. The test signal generator is comprised of means for providing a first test signal, which may be an alternating signal source ('A.C.'), and means for providing a second test signal, which may be a direct signal source ('D.C.'). The signal processor compares the signal from the transmission output of the filter during a direct signal phase with the signal from the transmission output of the filter during an alternating signal phase and produces the tuning control signal based on the comparison.

Frequency tuning apparatus and method for continuous-time filters

A preamplifier for use with currents developed by a photodetecting diode is disclosed wherein the currents are coupled to the base of an NPN transistor connected as a common emitter stage and a feedback resistor is connected by way of a buffer amplifier to the base to provide a standard transimpedance configuration. A control loop monitors the signal level by integrating the output of the buffer amplifier, and upon the detection of large signals the control loop causes a MOSFET in parallel with the feedback resistor to decrease the transimpedance and thereby increase the signal handling capability of the preamplifier. The control loop is also connected to a second MOSFET in parallel with the collector load resistor of said NPN transistor to decrease the effective collector load impedance for large signal levels. A third MOSFET in parallel with a resistor in the emitter of the NPN transistor is also responsive to the signal level in order to increase the amount of resistance in the emitter circuit of said common amplifier stage for large signal levels.

Optical transimpedance amplifier with high dynamic range

An amplifier arrangement suitable for use as a line driver is built with a Class AB stage connected in parallel with a Class B stage, whereby the output currents of the stages are summed. Each of the Class AB and the Class B stages has an output current device that is connected in a common-source configuration.

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Chatham Township, NJ, United States of America

Haideh Khorramabadi