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这里介绍一种适用于CMOS-IC中的自动转换偏置电压的电路。即使在输入电压超出电源电压时,它允许芯片衬底(或阱)在最高(或最低)电压下偏置。 在许多应用中,CMOS-IC的输入电压可能超出电路的正偏压或负偏压。当输入端和MOS晶体管的源或漏相连时,即使作为保护用途,也可能发生源(或漏)-衬底(或阱)二极管的正向偏置。如果输入源是低阻抗,功耗很大,很可能把电路烧毁。出于这种情况,需要控制芯片衬底的偏置电压,或需要控制晶体管和输入端相连区的偏压。采用p阱工艺和p沟输入晶体管,输入信号大于V_(DD)是危险的。相反,如果输入晶体管是n沟器件输入电压低于V将产生问题。采用n阱工艺,问题更多。在电源电压和输入电压之间自动转换衬底端压(或阱偏压)可以解决这些问题。
Here is a suitable CMOS-IC in the automatic conversion bias voltage circuit. It allows the chip substrate (or well) to be biased at the highest (or lowest) voltage even when the input voltage exceeds the supply voltage. In many applications, CMOS-IC’s input voltage may exceed the positive or negative bias of the circuit. When the input is connected to the source or drain of a MOS transistor, forward (or drain) - substrate (or well) diode forward biasing may occur even for protection purposes. If the input source is low impedance, power consumption is very large, it is possible to burn the circuit. In this case, it is necessary to control the bias voltage of the chip substrate or to control the bias voltage between the transistor and the connected region of the input terminal. Using a p-well process and a p-channel input transistor, it is dangerous that the input signal is greater than V DD. Conversely, if the input transistor is an n-channel device with a voltage below V, a problem arises. Using n-well process, the problem is more. These problems can be solved by automatically switching the substrate terminal pressure (or well bias) between the supply voltage and the input voltage.