Low noise transimpedance amplifier

Abstract

The invention discloses a low noise transimpedance amplifier. The amplifier comprises a main amplifier, an auxiliary amplifier, a transimpedance, two current sources, and a source follower. The main amplifier and the auxiliary amplifier adopt a cascode structure. The drain electrode of a common-source field-effect tube of the main amplifier is connected to the input end of the auxiliary amplifier.The output end of the auxiliary amplifier is fed back to the grid electrode of the common-grid field-effect tube of the main amplifier. The two current sources inject currents into the drain electrode of the common-source field-effect tube of a dual-stage amplifier. The input end of the source follower is connected to the output end of the main amplifier. The output end of the source follower isthe signal output end of the transimpedance amplifier. In the invention, main and auxiliary cascode amplifiers and a similar gain-boost structure are used to reduce a noise, and the two current sources inject the currents into the common-source field-effect tube so as to further reduce the noise; and a current gain control structure is used to adjust an excessive input current signal gain so thatthe dynamic range of a circuit is increased.

Description

technical field [0001] The invention relates to a transimpedance amplifier used in an optical receiver for passive optical network communication, in particular to a low-noise transimpedance amplifier. Background technique [0002] With the rapid growth of network data volume, transimpedance amplifier TIA (Transimpedance amplifier) ​​has been widely used in high-speed optical communication systems, especially in the field of passive optical network communication. The designed transimpedance amplifier should have the advantages of low noise, high gain, large bandwidth and small parasitic capacitance. In the optical receiver, the transimpedance amplifier converts the weak current signal output by the photodetector into a voltage signal, and performs preliminary amplification. Since the output current of the photodetector is usually very small, the equivalent input noise current of the transimpedance amplifier must be very small, otherwise its noise will overwhelm the signal an...

AI Technical Summary

Problems solved by technology

However, the cascode amplifier must have a higher power supply voltage to meet the voltage margin, and in an integrated circuit based on CMOS technology, as the size decreases, the parasitic effect of the circuit will increase significantly, and the cascode The bandwidth of the gate amplifier will be reduced due to the increase of input parasitic capacitance, which reduces the input point pole

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