| 摘要 |
1,166,352. Magnetic data storage apparatus; semi-conductor circuits. AMPEX CORP. 8 Aug., 1967 [8 Aug., 1966], No. 36431/67. Headings H3B and H3T. A sense amplifier, for a coincident-current read-out magnetic memory of the type having a common drive-sense line, includes means for eliminating the effect of the drive current in the amplifier during readout. A row driver supplies drive current to row drive winding 14 and dummy line 21 in parallel and due to imperfect matching of diodes 25, 26 this generally results in a voltage difference between inputs 30a, 30b to sense amplifier 30. The amplifier (Fig. 4) includes a differential amplifier stage 40 with transistors Q1 to Q8, preferably in integrated circuit form, providing an output at 40a, 40b. It is stated that the differential gain of the R5+R7 amplifier is . Transistors Q3, Q4 may R1 be omitted, and a temperature sensitive resistor may be connected across R1. Initially, when the row drive current has been initiated but before the column drive current is supplied, transistors Q9, Q10 of a clamp circuit 46 are conductive, earthing the emitters of these transistors. As a result capacitors C1, C2 are charged to voltages representing the amplified voltages at inputs 30a, 30b, but discriminator 42 receives no input. When column drive current is supplied the selected core 11 (Fig. 1) is switched and a signal input is supplied on line 14 to the sense amplifier. A strobe pulse is applied at 65 to the clamp circuit to switch off transistors Q9, Q10. The signal is then amplified in 40 and passed by the capacitors C1, C2 to discriminator 42 and output amplifier 44, while the effect of the drive currents on lines 14, 21 is eliminated by the previous charges on the capacitors. In order to allow the capacitors to charge to voltages of opposite polarities a second clamp circuit may be provided, including NPN transistors and controlled by a negative strobe pulse. |
