Semiconductor device

Abstract

A semiconductor device includes a phase compensation circuit 6 using a MOS capacitor with a structure in which an insulating film is disposed between a gate electrode formed on a semiconductor substrate and a diffusion layer. The phase compensation circuit includes first and second MOS capacitors 14, 15 . A gate electrode terminal of the first MOS capacitor is connected equivalently to a diffusion layer terminal of the second MOS capacitor that is a terminal opposite to the gate electrode terminal. A potential difference generating element 16 that generates a potential difference by allowing a current to flow therethrough is connected between a diffusion layer terminal of the first MOS capacitor and a gate electrode terminal of the second MOS capacitor. When the MOS capacitors having the voltage dependence are used, e.g., as a phase compensation circuit element of an operational amplifier, the MOS capacitance is not reduced, no matter the range of the input or output voltage of the operational amplifier, so that the phase margin will not reduced.

Description

technical field [0001] The present invention relates to a semiconductor device using a voltage-dependent MOS capacitor as a phase compensation circuit element such as an operational amplifier. Background technique [0002] In a conventional semiconductor device, when a MOS capacitor is used as a capacitor for phase compensation such as an operational amplifier, two MOS capacitors are used by connecting terminals of opposite polarities to each other in parallel. The MOS capacitor refers to a capacitor formed on a semiconductor substrate and having an insulating film (gate oxide film) structure between a gate electrode and a diffusion layer. Hereinafter, a "CMOS operational amplifier" disclosed in Japanese Patent Application Laid-Open No. 10-270957, which is a conventional semiconductor device, will be described with reference to FIG. 7 . [0003] In FIG. 7 , N-channel MOS transistor 87 and N-channel MOS transistor 88 constitute a differential input stage portion, and signals...

AI Technical Summary

Problems solved by technology

Therefore, for example, the voltage between the terminals of the phase compensation capacitor 86 of the operational amplifier in FIG. High chance of op amp oscillation

[0016] In addition, in order to avoid the possibility of oscillation even under the use condition that (VOUT-V1) becomes near 0V, it is necessary to make the phase compensation capacitor 86 very large, and there is a problem that the chip size becomes large.

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