Patent GB-860483-A (GB)
Title: Improved capacitor storage device
IPC: G11C11/402
Filed: 1957-10-16
Abstract: 860,483. Digital data storage apparatus. INTERNATIONAL BUSINESS MACHINE CORPORATION. Oct. 16, 1957 [Oct. 18, 1956], No. 32302/57. Class 106 (1). An electronic data storage device comprises a storage capacitor 22, Fig. 1, circuit means coupled to said capacitor and adapted to produce a voltage pulse on a lead 20 when said capacitor is storing a predetermined charge at the beginning of a read-out interval, including further circuit means responsive to said voltage pulse and coupled to said capacitor to prevent the alteration of the charge on said capacitor throughout said read-out interval. The capacitor 22 is said to be storing a 1 when it is not charged having both its plates at - 35 v., and to be storing a 0 when it is charged to 45 v., having its upper plate at 10 v. and its lower plate at - 35 v. To read out the bit stored on the capacitor 22 positive signals have to be applied simultaneously to terminals 34 and 44 and together with a negative signal applied to a terminal 80. The effect of the two positive signals is to bring junctions 38 and 46 both to a potential of 10 v., and hence a junction 24 and the top plate of the capacitor also are brought to a potential of 10 v. The effect of this depends upon the previous charge on the capacitor 22. If the capacitor were previously charged to 45 v. (storing a 0) then its upper plate will already be at a potential of 10 v. and nothing further happens, an output terminal 92 remaining at its normal low potential of - 35 v. If, however, capacitor 22 were previously charged to 0 v. (storing a 1) then its upper plate will be at a potential of - 35 v., and the effect of the two positive input signals on terminals 34 and 44 will be to cause a positive pulse to pass through the capacitor to the cathode of a normally conducting triode 52 which is thereby cut-off. This causes a cathode follower 54 to become highly conductive which, in turn, has a retroactive effect on triode 52 maintaining its cathode at a relatively high potential of 10 v. The cutting-off of triode 52 also causes the potential of the output terminal to rise to 10 v. thereby indicating the read-out of a 1. Thus when capacitor 22 is initially charged to 0 v. ( - 35 v. on both plates) the effect of the positive input signals on terminals 34 and 44 and the negative signal on terminal 80 is to cause an output signal at terminal 92, and also to cause the potentials on both plates of capacitor 22 to be raised to 10 v. so that the capacitor remains charged to 0 v. At the end of the read-out period the positive signals on terminals 34 and 44 and the negative signal on terminal 80 cease, a triode 78 conducts, thereby cutting-off cathode follower 54, which in turn allows conduction to recommence in triode 52 and capacitor 22 returns to its original state with a potential of - 35 v. on each plate. To read-in a bit an input signal is applied to a terminal 10 (positive 10 v. for 1 and a normal -- 35 v. for 0), positive signals are applied to terminals 34 and 44, as for read-out, and the potential on terminal 80 is maintained at its normal relatively high potential of 10 v., thereby preventing cathode follower 54 from conducting.