A circuit and method for eliminating output DC offset

Abstract

The invention relates to a circuit and method used for eliminating the output direct-current offset. The circuit comprises a pre-stage amplification circuit, an amplitude detection circuit, a detector circuit, an adjusting current generating circuit and a direct-current correction circuit, which are successively connected. The pre-stage amplification circuit is connected with the direct-current correction circuit. According to the invention, by properly setting resistance values of related resistors, the offset voltage of differential signals in different offset degrees can be eliminated. The amplitude of an original signal is firstly detected, then, the adjusting value is calculated according to the amplitude of the original signal, and the original signal is adjusted by use of the calculated adjusting value. Thus, real-time adjustment can be performed when the amplitude of the original signal is changed, so the circuit and the method are flexibly and widely applied.

Description

technical field [0001] The invention relates to integrated circuit design, in particular to a circuit and method for eliminating output direct current offset. Background technique [0002] In integrated circuit design, for amplifier circuits with differential input, it is generally required that the common-mode point of the two differential input signals be biased at a potential V CM ,like figure 1 As shown, this allows the amplifier circuit to be biased in normal operation. [0003] However, sometimes the front-end circuit cannot generate differential signals with the same common mode point, but there will be output DC offset, such as the output waveform of the differential transimpedance amplifier, such as figure 2 As shown, high-frequency applications often use AC coupling to solve the above problems, that is, there are two differential signals with DC offsets. After passing through the coupling capacitor and adding the bias circuit of the subsequent stage, a different...

AI Technical Summary

Problems solved by technology

[0003] However, sometimes the front-end circuit cannot generate differential signals with the same common mode point, but there will be output DC offset, such as the output waveform of the differential transimpedance amplifier, such as figure 2 As shown, high-frequency applications often use AC coupling to solve the above problems, that is, there are two differential signals with DC offsets. After passing through the coupling capacitor and adding the bias circuit of the subsequent stage, a differential signal with a common-mode point biased at one potential is formed. Signal

[0004] However, in low-frequency applications, a very large coupling capacitor is required to achieve a better DC blocking effect, which is impossible to integrate on-chip. If an off-chip capacitor is used, monolithic integration cannot be achieved, and at the same time, the cost is increased.

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