| 摘要 |
PURPOSE:To control the size of a transistor in an input buffer circuit by providing an inverter circuit consisting of two conductive type MOS transistors that are serially connected with each other and at least one additional conductive type MOS transistor and inputting the prescribed signal to an external control pin. CONSTITUTION:When a low level signal is inputted to a control terminal A, transistors 5 and 6 are turned ON and OFF, respectively, and signals from an input terminal I are inputted to gate terminals in transistor 1, 2 and 3 in common. The sizes of the P channel transistors 1, 3 and 5 become ones obtained by adding three to the transistor 1. Similarily, when a high level signal is inputted to the control terminal A, the transistors 5 and 6 are OFF and ON, respectively, and the signals from the input terminal I are inputted to the gate terminals in the transistors 1, 2 and 4. Then the sizes of the N channel transistors 2, 4 and 6 become ones obtained by adding four to the transistor 2. Even if the type of an external integrated circuit is modified, no remodeling of said integrated circuit is needed.
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