| 摘要 |
<p>PURPOSE:To change the set of an active level by switching a first active level setting circuit and a second active level setting circuit, which is set at the level reverse to that of the first active level setting circuit, by a switching circuit. CONSTITUTION:Since a nodal point Node D is set to an 'L' level in the state of conducting a polysilicone (Poly-Si) fuse 3, an N channel transistor Tr 2 is turned ON and the output of a first active level setting circuit 1 is inputted to a NAND circuit NA1 and a NOR circuit NR1. Then, an OE terminal is set to an 'H' active terminal. When it is necessary to change the level, a high voltage is impressed from an external terminal IN2. When the Poly-Si fuse 3 is cut off, the nodal point Node D is changed from the 'L' level to an 'H' level and the transistor Tr 2 is turned OFF. Thus, an output 'L' of a second active level setting circuit 2 is inputted to the NA1 and the NR1 and this OE terminal is changed to an 'L' active terminal. In such a way, the active level can be easily changed.</p> |
