Patent ID: 6583748
Filing Date: 2003-06-24
Classification: H01L,H03K

Abstract:
Analog input selection circuit comprising:a plurality of analog input selection units formed on an identical P-type semiconductor substrate, each of the analog input selection units including an input terminal, an output terminal, a transmission path extending between the input terminal and the output terminal, wherein an analog voltage signal is input into the input terminal; transmission switches which allow the analog voltage signal to pass through the transmission path when that particular analog input selection unit is selected, and which does not allow the analog voltage signal to pass through the transmission path when that particular analog input selection unit is not selected; an over-voltage protection switch which allows the analog voltage signal to pass to the ground when that particular analog input selection unit is selected, and which does not allow the analog voltage signal to pass to the ground when that particular analog input selection unit is not selected; a PMOS transistor provided between the input terminal and a power supply, and which flows an undesired current generated by a positive over-voltage applied to the input terminal, to the power supply; and an NMOS transistor provided between the input terminal and the ground, and which flows an undesired current generated by a negative over-voltage applied to the input terminal, to the ground, wherein a region in which the NMOS transistor is formed in each of the analog input selection units is surrounded by an N-well region.