| With the continuous development of the modernization process,the demand for communication is getting higher which requires not only the communication speed is faster,but also the transmission distance is farther.Traditional wire transmission loss and its small capacity have been unable to meet the requirements of the Internet development.Optical fiber communication rises sharply with wide bandwidth,large capacity,long transmission distance and anti-jamming advantages.In recent years,fiber to the home(FTTH),the chip interconnection,LAN and optical network have entered people’s daily lives,greatly improving the quality of life.In optical fiber communication system,the preamplifier is the most important part of the front-end amplifier.This topic uses the 5 5nm CMOS technology to design the communication rate 2.5Gbps ultra high sensitivity preamplifier.This chip is used in the optical fiber transmission and its speed class in the international synchronous digital system is STM-16.As the front-end optical receiver preamplifier circuit,its performance determines the performance of optical receiver,which has a great influence on limiting amplifier and the recovery of clock circuit,so it is the most difficult circuit to design and the performance index is also relatively harsh.The performance index of the 2.5Gbps transimpedance amplifier designed in this paper is as follows.Its differential transimpedance gain is 40K,the equivalent input noise current is 96nA,the low cut-off frequency is 20KHz,the high cut-off frequency is 1.85GHz,the sensitivity is-30.2dBm,the input dynamic range is 30dB,the input saturation current is 2mA and the current power consumption is 36.2mA,The whole chip uses the 3.3V standard power supply voltage.The preamplifier adopts the design concept of sub module,mainly divided into the core amplifier and bias circuit.The core circuit mainly includes the input stage,the single ended to differential amplifier stage,the differential amplifier stage,the output buffer stage,the automatic gain control module,the input current monitor module,and the photodiode supply voltage module.The bias circuit mainly includes a bandgap circuit,a main power supply circuit and a current bias circuit.The input stage converts the input optical current into voltage output,used for signal processing.The single ended to differential amplification stage converts the single ended voltage generated by the input stage to the differential voltage output to facilitate the connection with the second stage.The differential amplifier stage mainly amplifies the voltage signal,and can drive the output buffer stage.The output buffer stage is mainly driven by a 50 ohm load at the back stage to provide a large output amplitude to avoid electromagnetic interference.The bandgap circuit mainly improves a temperature independent voltage and a current proportional to the temperature.The main power supply circuit converts the output voltage of the bandgap circuit into a voltage source which can be loaded.The current bias circuit mainly provides multiple current output. |
