Offset compensation structure suitable for large-dynamic-range logarithmic amplifier

Abstract

The invention belongs to the field of integrated circuits, and particularly relates to an offset compensation structure of a large-dynamic-range logarithmic amplifier chip. The offset compensation structure comprises a first-stage limiting amplifier, a multi-stage limiting amplifier, a transconductance detection unit, a constant current source and a feedback current source; the first-stage limiting amplifier is respectively connected with the input positive end and the input negative end of a differential signal, and the output positive end and the output negative end of the differential signal are connected with the input positive end and the input negative end of the multi-stage limiting amplifier; the constant current source is connected with the input negative end of the multi-stage limiting amplifier, and the feedback current source is connected with the input positive end of the multi-stage limiting amplifier; the transconductance detection unit is connected with the output negative end and the output positive end of the multi-stage limiting amplifier; according to the invention, the transconductance detection unit is used for obtaining a difference result between the voltage of the output positive end and the voltage of the output negative end, the feedback current is generated through the feedback current source, the current of the constant current source compensates the direct current working point change of the first-stage limiting amplifier caused by the feedback current, and the effect of stabilizing the working of the limiting amplifier is achieved.

Description

technical field [0001] The invention belongs to the field of integrated circuits, in particular to an offset compensation structure of a logarithmic amplifier chip with a large dynamic range. Background technique [0002] The topology of a high dynamic range log amp is as figure 1 As shown, it uses six limiting amplifiers connected in series, and rectification is performed at the output of each limiting amplifier, and the rectified current is added to obtain the total rectified current, and then the rectified current signal is converted into an output voltage through the transimpedance output stage . Through this structure, an output voltage that has a linear relationship with the input power can be obtained. [0003] The structure of the limiting amplifier is as figure 2 As shown, it is essentially a differential pair with a resistor as a load. Q1 and Q2 constitute a differential input pair of transistors, and the bases of Q1 and Q2 are respectively connected to the po...

AI Technical Summary

Problems solved by technology

[0007] Based on the problem that the total gain of the limiting amplifier in the logarithmic amplifier is too high and it is easy to cause DC mismatch, resulting in out-of-tolerance parameters and abnormal functions of the logarithmic amplifier.

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