Off-centre compensation circuit and off-centre compensation method

Abstract

An offset compensation circuit comprises an A / D converter, a D / A converter, an attenuator and an analog adder. The A / D converter measures the DC level of an inverting type analog output buffer arranged in an analog signal processing circuit and converts the obtained analog signal into a digital signal. The D / A converter receives the digital signal output from the A / D converter as input and converts the digital signal into an analog signal. The attenuator receives the analog signal output from the D / A converter as input and attenuates its amplitude. The analog adder receives the output signal of the attenuator and that of the analog signal processing circuit as inputs, adds the two signals and supplies the sum signal to the inverting type analog output buffer as input signal of the latter.

Description

technical field [0001] The present invention relates to an offset compensation circuit and an offset compensation method for compensating a DC offset of an output signal in an analog signal processing circuit, and is suitable for, for example, an LSI for analog front-end signal processing for CD players and DVD players, A circuit in which output DC offset affects operation and performance. Background technique [0002] Generally, a DC input offset in a single operational amplifier is caused by variation in matching of characteristics of transistors constituting an input differential stage. Variations in the characteristics of transistors are caused by the manufacturing process of transistors, and in the case of MOS transistors in particular, it is difficult to improve only in the manufacturing process. [0003] Therefore, a method for compensating the DC input offset on the circuit has been developed, for example, through ICL 7650 (INTERSIL Company), MAX 430, 432 (Maxim Com...

AI Technical Summary

Problems solved by technology

In such an application field, it is not uncommon to use dozens of amplifiers as a whole of the LSI, so an increase in the circuit scale when using a chopper stabilizer type amplifier is unavoidable, especially when using MOS transistors to realize the above analog When using LSI for front-end signal processing, etc., there will be a big problem

[0013] Moreover, since the above-mentioned increase in chip size and switching noise generated by the chopping clock must be considered, design complexity such as selecting the frequency of the chopping clock is inevitable.

Also, related to this switching noise, while it is possible to reduce the effect, it is impossible to have no effect

[0014] Also, in the case where the frequency of the input signal is close to the frequency of the chopping clock, there is a problem of mutual modulation in which the input signal is modulated by the frequency of the chopping clock

This means that the frequency range of the input signal is limited in product application, and there is a problem of narrowing the use range

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