Transimpedance amplifier with bandwidth extender

Abstract

A transimpedance amplifier with an input configured to receive a current input from an upstream device and output configured to present an output voltage. In one configuration, there are three amplifier stages in the transimpedance amplifier connected in series. A feedback path with feedback resistor connects between the input and output of the transimpedance amplifier. A bandwidth extender circuit connects between a stage output and a stage input of the transimpedance amplifier. In a three-stage embodiment, the bandwidth extender circuit extends between an input of the second stage and the output of the second stage. The bandwidth extender includes at least one active device configured to provide positive feedback to increase gain. The bandwidth extender circuit may be automatically or selectively deactivated to filter unwanted frequency components.

What is claimed is: 
     
         1 . A transimpedance amplifier comprising:
 a transimpedance amplifier having a transimpedance amplifier input and a transimpedance amplifier output, the transimpedance amplifier input configured to receive an input signal, the transimpedance amplifier including;   a first stage comprising a transistor and a load element, the first stage connected to receive the input signal and having a first stage output;   a second stage comprising a transistor and a load element, the second stage connected to the first stage output and having a second stage output;   a third stage comprising a transistor and a load element, the third stage connected to the second stage output and forming the transimpedance amplifier output;   a first feedback loop including feedback resistor, the feedback loop connected between to the transimpedance amplifier output and the transimpedance amplifier input; and   a bandwidth extender including an active element, a bandwidth extender connected between the first stage output and the second stage output.   
     
     
         2 . The transimpedance amplifier of  claim 1 , wherein the active element in the bandwidth extender is a FET such that the FET has a gate terminal connected to the second stage output and a drain terminal connected to the first stage output. 
     
     
         3 . The transimpedance amplifier of  claim 1 , wherein the bandwidth extender is configured to provide positive feedback from the second stage output to the first stage output to increase the gain of the transimpedance amplifier. 
     
     
         4 . The transimpedance amplifier of  claim 1  further comprising a switch configured to receive an enable signal that selectively enables or disables the bandwidth extender. 
     
     
         5 . The transimpedance amplifier of  claim 1  wherein the first stage, second stage, and third stage include a FET acting as an amplifier and an active load or a passive load. 
     
     
         6 . A transimpedance amplifier comprising:
 an input configured to receive a transimpedance amplifier input signal;   one or more amplifiers stages, each of the one or more stages having a stage input and a stage output;   a bandwidth extender connected between a stage output and a stage input, the bandwidth extender including at least one active device configured to provide positive feedback from the stage output to the stage input.   
     
     
         7 . The transimpedance amplifier of  claim 6  wherein the bandwidth extender is configured to be selectively enabled and disabled. 
     
     
         8 . The transimpedance amplifier of  claim 7 , wherein the selective enabling and disabling is responsive to a control signal. 
     
     
         9 . The transimpedance amplifier of  claim 6 , wherein disabling the bandwidth extender filters out high frequency content of a laser relaxation oscillation signal. 
     
     
         10 . The transimpedance amplifier of  claim 6 , wherein the one or more stages comprise one stage with an input and an output, and the bandwidth extender is connected between the one stage input and the one stage output. 
     
     
         11 . The transimpedance amplifier of  claim 6 , wherein the one or more stages comprise a first stage, a second stage, a third stage, a fourth stage and a fifth stage, with each stage having an input and an output, and the bandwidth extender is connected between a second stage input and a fourth stage output. 
     
     
         12 . A method for processing an input current with a transimpedance amplifier to generate a corresponding amplified voltage comprising:
 receiving the input current at a first stage amplifier of the transimpedance amplifier, the transimpedance amplifier having one or more amplifier stages that includes a first stage amplifier;   receiving a feedback signal from a feedback path at the first stage amplifier, the feedback path including feedback resistor;   amplifying the feedback signal and the input current with the one or more amplifier stages to generate a transimpedance amplifier output signal;   presenting the transimpedance amplifier output signal as an input to the feedback path;   performing bandwidth enhancement by amplifying an amplifier stage output signal from one or more of the one or more amplifier stages and presenting the amplified amplifier stage output signal as positive feedback to an input of the one or more amplifier stages to increase the gain of at least one amplifier stage of one or more amplifier stages of the transimpedance amplifier to thereby increase the bandwidth of the transimpedance amplifier.   
     
     
         13 . The method of  claim 12 , further comprising receiving a control signal to selectively enable or disable bandwidth enhancement. 
     
     
         14 . The method of  claim 12  further comprising detecting unwanted high frequency content in the transimpedance amplifier input and responsive thereto disabling the bandwidth enhancement. 
     
     
         15 . The method of  claim 12  wherein the one or more stages comprises three stages. 
     
     
         16 . The method of  claim 12  wherein the transimpedance amplifier operates at multi-data rates, higher or lower than 2.5 Gbps. 
     
     
         17 . The method of  claim 12  wherein the method is performed in a ROSA or other type optical packages of a passive optical network. 
     
     
         18 . The method of  claim 12  wherein performing bandwidth enhancement occurs by amplifying an amplifier stage output signal.