| 摘要 |
1,243,676. Transistor bi-stable circuits. COMMISSARIAT A L'ENERGIE ATOMIQUE. 2 Dec., 1968 [14 Dec., 1967], No. 57092/68. Heading H3T. A first emitter coupled pair of transistors 24, 26 has its collectors connected to respective bases of a second emitter coupled pair 36, 34, one transistor 34 of which is cross-coupled with one 26 of the first pair to give a threshold whose value (v 2 -v r ,Fig. 3, not shown) is determined by a current source transistor 42, and is equal to the hysteresis voltage (v 2- v 1 ). This transistor 42 is controlled through a transistor 44 by the setting of a potentiometer 50, which also sets the standing D.C. level (v r ) at the base of T24 to be the same as the lower threshold limit. Transistors 26, 36 are normally on, 24, 34 off; when an input signal (Fig. 3, not shown) at 56 goes above earth, T24 turns on and T26 off. Regenerative switching between T34, T26 speeds the process, and T36 turns off to produce an output. Resetting occurs when the input falls to make T24 base lower than the collector voltage of T34 which is the lower limit of the hysteresis and depends (inter, alia) upon the T42 current. In another embodiment (Fig. 6, not shown), a constant current transistor (72) is provided in the emitter circuit of the first emitter-coupled pair (64, 66); the second emitter-coupled pair and their variable current source transistor (86, 88, 94) being in this case PNP type, and the other connections being functionally similar to Fig. 5. In this case the potentiometer (104) adjusting the current in the second pair (86, 88) does not vary the D.C. standing level of the input transistor, and it is the upper limit of the threshold (v 2 ) which is now variable. |
