Capacitance compensation circuit and analog-digital converter for NMOS input transistor of operational amplifier

Abstract

The invention provides a capacitance compensation circuit for an NMOS input transistor of an operational amplifier. The capacitance compensation circuit is a deep N-well NMOS transistor. The invention further provides an analog-digital converter. A differential signal of the operational amplifier of the analog-digital converter uses the NMOS transistor as an input transistor. The capacitance compensation circuits are arranged at two input ends of the operational amplifier. The structure of the NMOS input transistor of the operational amplifier is the same as that of the deep N-well NMOS transistor. The gate of the deep N-well NMOS transistor is connected with the gate of the NMOS input transistor of the operational amplifier to be used as an input end VP / VN of an input signal of the operational amplifier. The source and the drain of NM1 of the deep N-well NMOS transistor are connected with a P-well and is connected with a positive voltage V1 which is more than a threshold voltage VTHN of the deep N-well NMOS transistor, and the substrate of the NMOS input transistor of the operational amplifier is grounded. The capacitance compensation circuit provided by the invention could enable stray capacitances CCP and CCN of the two input ends of the operational amplifier to be equal and to maintain a relative constant value, thereby improving performance of the operational amplifier or the analog-digital converter.

Description

technical field [0001] The invention belongs to the technical field of analog integrated circuits, in particular to a capacitance compensation circuit for an operational amplifier NMOS input tube, and is particularly suitable for the field of analog-to-digital converters. Background technique [0002] In recent years, with the further improvement of the performance indicators of analog integrated circuits, especially with the continuous development of integrated circuit technology, the research on operational amplifiers has become more and more in-depth. Although the traditional upper plate direct sampling technology can reduce the capacitance of the capacitor array, since the capacitance of the parasitic capacitance at the input of the operational amplifier changes with the voltage at the input of the operational amplifier, it will affect the actual matching accuracy of the capacitor array. As a result, the overall performance of the analog-to-digital converter is affected,...

AI Technical Summary

Problems solved by technology

This will produce a non-linear error for the operational amplifier AMP or the analog-to-digital converter

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