A Limiting Amplifier with On-chip DC Offset Cancellation

Abstract

The invention discloses a limiting amplifier allowing a direct-current offset eliminating function to be achieved on a sheet. The limiting amplifier comprises an input circuit, an amplifying circuit, an output circuit and a direct-current negative feedback circuit. The direct-current negative feedback circuit comprises a first amplifier, a second amplifier, a first capacitor, a second capacitor, a first resistor and a second resistor. The first amplifier, the second amplifier, the first capacitor and the second capacitor form a closed loop. Direct-current offset of the amplifying circuit is fed back to the input circuit to be used for eliminating direct-current offset of the circuits after being sampled through a low-pass filter formed by the first resistor, the second resistor, the first capacitor and the second capacitor of the direct-current feedback circuit, and amplified through the first amplifier. According to the limiting amplifier, a direct-current offset eliminating circuit is obtained through the small capacitors on the sheet, and the phenomenon that error codes are produced when low-frequency cut-off frequency is excessively high due to the direct-current offset eliminating circuit can not occur even when a long string of 1 signals or a long string of 0 signals are processed.

Description

technical field [0001] The invention relates to a limiting amplifier applied in the field of optical communication, in particular to a limiting amplifier with high gain bandwidth and on-chip DC offset elimination function. Background technique [0002] With the rapid development of computer network, the wide application of multimedia communication and the large-scale construction of information superhighway, people's demand for high-speed communication system is getting higher and higher. Passive optical network has become the most attractive solution because of its high bandwidth, low cost, anti-interference and other advantages. As an important part of the optical receiver, the limiting amplifier's main function is to further amplify the smaller voltage signal provided by the pre-stage transimpedance amplifier for use by the post-stage clock recovery circuit. [0003] figure 1 Shown is a traditional limiting amplifier, mainly consisting of an input stage, multiple gain s...

AI Technical Summary

Problems solved by technology

While stabilizing the DC level of the circuit, the DC negative feedback network introduces a low-frequency cut-off frequency to the AC characteristics of the circuit. Too high a low-frequency cut-off frequency will cause the output terminal to be amplified when the continuous "1" or continuous "0" is amplified. Drift occurs, which eventually leads to bit errors

In order to overcome this problem, the value of the resistance and capacitance of the low-pass filter in the DC negative feedback network is usually increased, but the capacitance area is too large to be realized on-chip, so the traditional method is to use an off-chip capacitor

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