A low noise transimpedance amplifier for optical receiver.

Area of Science:

• Electrical Engineering
• Analog Integrated Circuit Design

Background:

• Transimpedance amplifiers (TIAs) are crucial for converting photodiode current to voltage.
• Optimizing TIA noise performance and bandwidth is essential for high-speed optical receivers.
• Traditional designs often face trade-offs between gain, bandwidth, and noise.

Purpose of the Study:

• To enhance the noise characteristics and gain-bandwidth product of a transimpedance amplifier.
• To integrate a regulated cascode (RGC) structure with a shunt-feedback TIA without adding noise sources.
• To achieve high-speed data rates with improved amplifier performance.

Main Methods:

• Cascading a regulated cascode (RGC) structure with a shunt-feedback transimpedance amplifier.
• Optimizing metal-oxide-semiconductor (MOS) sizes and increasing transimpedance gain.
• Analyzing average input-referred noise current.
• Incorporating a π-type matching network with an added inductor.

Main Results:

• Achieved a transimpedance gain of 59.5 dBΩ and a -3 dB bandwidth of 4 GHz.
• Demonstrated an average input-referred noise current spectral density below 7 pA/√Hz.
• Attained a data rate of 5 Gb/s with a photodetector capacitance of 300 pF and 1.8 V supply voltage.

Conclusions:

• The cascaded RGC and shunt-feedback TIA effectively improves gain-bandwidth product.
• The optimized circuit achieves excellent noise performance and high data rates.
• The design offers a robust solution for high-speed optical communication systems.