| 摘要 |
701,018. Semi-conductor gating circuits. TELEFONAKTIEBOLAGET L. M. ERICSSON. Oct. 5, 1951. [Oct. 12, 1950], No. 23285/51. Class 40 (6) A switching circuit comprises two oppositely poled series rectifiers (preferably of the drycontact type) and a shunt rectifier connected to the common point of said first two rectifiers, and means for applying a switching potential to said common point, whereby the series arm is conducting and the shunt arm non-conducting or vice versa in accordance with the value of the switching potential. As shown, Fig. 4, two parallel T-networks are provided for gating signals of positive and negative polarities respectively. Normally the upper T-network is closed due to the back biasing of rectifiers 12, 13 from the source 16 and the forward biasing of rectifier 20 due to the point 16 being at a higher biasing potential than the point 17. If, however, a negative pulse of sufficient amplitude is applied to the point 26 rectifiers 12 and 13 become forward biased and rectifier 20 becomes back biased. The upper T-network will then pass positive signals from point 1 to point 3 but negative signals will be subject to clipping. A circuit comprising oppositely poled diodes 14, 15 and 23 and fed at point 29 with positive pulses is therefore provided for gating the negative signals. In the arrangement shown in Fig. 6 the gating pulses are derived by connecting a single source of pulses to a transformer 33 having two oppositely poled secondary windings for pulsing the upper and lower T- networks. If the rate of pulsing is sufficiently rapid the biasing source at 16, 17 may be dispensed with, the biasing voltage being derived from the condenser 38 which is charged by the rectifying action of the diodes on the pulses. In a further embodiment, Fig. 7, two identical T- networks are connected between corresponding pairs of terminals of the input and output transformers 39, 40. The networks are pulsed from a common source over resistors 41, 42. Capacitors 46, 47 provide a low impedance path for the pulses if the transformer 39 is designed for low frequencies and would consequently present a high impedance to the pulses. Specification 482,103 is referred to.
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