Circuit for calibrating operational amplifier imbalance in successive approximation register mode

Abstract

The invention discloses a circuit for calibrating operational amplifier imbalance in a successive approximation register mode. The circuit comprises an operational amplifier module, a comparer module, a control logic unit, a four-digit successive approximation register and a four-digit DAC module. The in-phase end of the comparer module is connected with an output voltage of the operational amplifier module. The inverted phase end of the comparer module is connected with VDD / 2. The output end of the comparer module is connected with the logic control unit. The output end of the logic control unit is connected with the four-digit successive approximation register. Four output ports of the four-digit successive approximation register are connected with four input ends of the four-digit DAC module. The voltage output end of the four-digit DAC module is connected with the operational amplifier module. The imbalance is calibrated in the successive approximation register (SAR) mode, a calibration process can be finished only through clock periods of which number is the same to the number of calibration digits, and the calibration speed is improved.

Description

technical field [0001] The invention belongs to the field of CMOS process integrated circuits, and in particular relates to a circuit for correcting operational amplifier offset by successive approximation. Background technique [0002] In the preparation process of the operational amplifier, due to the uncertainty of the manufacturing process, it is inevitable that a certain amount of offset will be caused by random errors. In the amplifying circuit based on the operational amplifier, the offset of the operational amplifier will have a great impact on the accuracy of the amplifying circuit, especially in the DC small signal amplifying system. There are many ways to reduce or eliminate this offset voltage, such as increasing the size of input transistors and active loads, using self-zeroing techniques, and chopping techniques. However, no matter which method is adopted, there are more or less problems, such as a large parasitic capacitance or a requirement for the operating...

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Problems solved by technology

At present, there are methods to solve the problems caused by the above solutions, but if the accuracy of offset correction is to be improved, the correction time will inevitably be increased, which brings about the problem of too long start-up time of the op amp

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