| 摘要 |
PURPOSE:To reduce a manufacturing cost by providing connecting and nonconnecting means between the emitter of a transistor of a power source side and the collector of a transistor of a ground side, so that only one kind of a tristate type or an open collector type can be manufactured. CONSTITUTION:When manufacture is ended in a state of a figure (a), a program cell PC is in an open state, and a circuit in the figure is equivalent to that which is constituted of only resistances R1, R2 and TRs Q1, Q3, and operated as an open collector type TTL circut. In case when this circuit is used as a tristate type TTL circuit, when the base potential of the TR Q1 is made low and cut off, and a negative current pulse is applied to an output teminal OUT, a large current flows to a ground terminal through a TR Q2 of an on-state, the cell PC, a diode D and the TR Q3 from a power source Vcc, and a P-N junction of the cell PC is broken down and short-circuited. That is to say, it becomes as shown in a figure (b), and operates as a tristate type TTL circuit. |
