Yamaha Corporation

Terumitsu Maeno

Nobuaki H Tsuji

Masao Noro

Seiji Hirade

A lateral PNP transistor PB and a lateral NPN transistor NB are serially connected between an input terminal and a reference potential (ground potential). In the transistor PB, a diode Dis formed. In the transistor NB, a diode Dis formed. When an ESD of +2000 V is input, the transistor NB turns on, whereas when an ESD of &#x2212;2000 V is input, the transistor PB turns on. The level of a positive signal capable of being input is limited by the inverse breakdown voltage (e.g., 18 to 50 V) of the diode D, whereas the level of a negative signal capable of being input is limited by the inverse breakdown voltage (e.g., 13 to 15 V) of the diode D.

Semiconductor input protection circuit

An input protection circuit is provided which has a high electrostatic discharge (ESD) breakdown voltage and can input a signal in a wide positive and negative voltage range. In a surface layer of a substrate, a well and a field insulating film are formed. An emitter region is formed in the well to form a lateral bipolar transistor having the well as its base. Another emitter region is formed in the surface layer of the substrate to form another lateral bipolar transistor having the well as its collector. A gate electrode layer is formed on the field insulating film between the well and the other emitter region to form a MOS transistor. The emitter region is connected to an input terminal, the well is connected to the gate electrode layer, and the other emitter region and substrate are connected to a ground potential.

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Iwata, Japan

Terumitsu Maeno