The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 02, 1996
Filed:
Dec. 21, 1994
Haideh Khorramabadi, Chatham Township, Morris County, NJ (US);
Maurice J Tarsia, Colonia, NJ (US);
Liang D Tzeng, Fogelsville, PA (US);
AT&T Corp., Murray Hill, NJ (US);
Abstract
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.