Voltage limiting apparatus as well as operation amplifier applying the same and circuit design method thereof

Abstract

A voltage restraint device which is applied in an operational amplifier comprises a first transistor; the trans-voltage of a gate and a source approaches to a certain voltage and the trans-voltage of a drain and the source is not equal to zero, thereby leading to a larger substrate electric current. The voltage restraint device comprises a second transistor; the source is coupled to the drain of the first transistor; the gate receives bias signals, which leads the second transistor to be operated in a saturation region and leads the source voltage of the second transistor is equal to the gap between the bias signals and the threshold voltage of the second transistor; therefore, the electric current of the substrate can be reduced by reducing the trans-voltage of the drain of the first transistor and the source.

Description

technical field [0001] The present invention relates to a voltage limiting device, and in particular to a voltage limiting device capable of reducing the substrate current of a transistor in an operational amplifier (Operational Amplifier) ​​and its adverse effects. Background technique [0002] The liquid crystal display includes a source driver (Source Driver), a gate driver (GateDriver) and a liquid crystal display panel, wherein the liquid crystal display panel has a pixel array, and the source driver is used to provide pixel data to the pixel array. The corresponding pixel column in the pixel array is turned on sequentially to display the image to be displayed. Please refer to figure 1 , which shows a plot of the substrate current of a transistor in an operational amplifier versus its bias voltage. Traditionally, the operational amplifier (Operational Amplifier) ​​is used to realize the output buffer of the source driver, and some transistors (Transistor) will be affe...

AI Technical Summary

Problems solved by technology

[0003] Part of the hot electrons will flow to the gate of the transistor and be trapped in the gate oxide layer (GateOxide), causing the threshold voltage (Threshold voltage), saturation current and characteristics of the transistor to change over time, eventually causing it to malfunction ( Malfunction), so that the traditional operational amplifier and its source driver also have the disadvantage of short product life

[0004] The higher substrate current will also increase the DC operating current of the traditional operational amplifier and its source driver, which will cause the traditional operational amplifier and its source driver to have the disadvantage of high power consumption; and if it is used in On portable (Portable, or portable) products, it will lead to the disadvantage of poor endurance of portable products

[0005] A higher substrate current is more likely to lead to a continuous increase in the substrate voltage, causing the parasitic transistors in it to be forward-conducted, resulting in a latchup effect or a snapback effect, resulting in greater substrate current and hot electrons, making the above disadvantages more serious

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