| 摘要 |
957,101. Tunnel diode logic circuits. RADIO CORPORATION OF AMERICA. July 24, 1961 [Aug. 22, 1960], No. 26794/61. Heading H3T. [Also in Division G4] A binary half adder circuit comprises two parallel branch circuits, each including a transistor, negative resistance means being included in at least one of said branch circuits for steering operating current into one or the other of said branch circuits in accordance with the number of pulses received concurrently. As described, a half adder comprises two parallel branch circuits, a first branch including a transistor 24 and a second branch including a transistor 16 and tunnel diodes 14, 18. The characteristic for the second branch is shown at 57, 58, 59, 60, 61, 62, Fig. 4, and is correct for no input pulses or just one input pulse applied to the input terminals 30, 32. If two input pulses are applied simultaneously, the transistor 24 conducts and the characteristic 57-62 of Fig. 4 is changed. Current is supplied from a constant current source 10 which current may be a steady D.C. or in the form of pulses coincident with the -information pulses. With no input pulses applied, the circuit operates at point 72, the tunnel diode 18 being in a low voltage state and steering the current into the tunnel diode 18 so that none flows into the transistor 16. When one input pulse is applied to terminals 30 or 32, the load line for resistors 34, 36 shifts to the dotted position 74 and there is no stable intersection corresponding to point 72 so that the operating point shifts to 76 where the tunnel diode 18 is in its high voltage state thereby causing the transistor 16 to conduct and an output representing " 1 " to appear at the sum terminal 42. When input pulses are applied to terminals 30, 32 simultaneously, the tunnel diode 14 switches to the low current region of its high voltage state and the tunnel diode 18 therefore switches back to its low voltage state to cut off the transistor 16. The tunnel diode 14, however, in its high voltage state, turns the transistor 24 on to cause an output representing " 1 " to appear at the carry terminal 46. The circuit may be reset by a negative pulse from a source 38. In a slightly modified circuit (Fig. 2, not shown) the tunnel diode 18 is connected between the anode of the tunnel diode 14 and earth. |
