| 摘要 |
PURPOSE:To save power consumption and to improve the mounting density by the constitution that an output of a transistor/transistor (TR) logical circuit takes a tri-state level including high impedance by controlling a base potential of two PNP TRs. CONSTITUTION:When a point P is brought into a high level, a point 0 goes to a low level, points k and l are suppressed respectively to a level higher by VBE's share of T20, T21 from the level of the point 0, but this potential is a level sufficiently lower to turn off T16, T17 and T18, T19, and an output point (m) goes to a high impedance state. Most of a current flowing to R15 and R16 flows to ground from each collector of T20, T21, and a current flowing to a base is brought into a far smaller value than the emitter current by the effect of current gain. Thus, the current absorbing capability of a T23 is not so much required as being needed for a conventional circuit, the area is suppressed low and the power consumption of the control circuit itself is saved by the decrease in the scale of TRs. |
