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Driver With an AC Feedback Circuit

IP.com Disclosure Number: IPCOM000041683D
Original Publication Date: 1984-Feb-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Reinhart, GR: AUTHOR

Abstract

In a pulse capacitive driver the feedback is improved by feeding back from a circuit parallel to the output circuit of the driver rather than from the output circuit. This arrangement reduces the interaction between positive and negative transitions in the driver, and eliminates, or at least significantly attenuates, an effective voltage pulse produced in an external load from the driver output circuit during normal down-level operation. As shown in the figure, the driver includes an enhanced alternating current (AC) feedback circuit FC having Darlington pair transistors T1 and T2, an off-drive resistor R1, an off-drive diode D1 and a capacitor T7, formed from a transistor arrangement, connected between the base of transistor T3 and the base of transistor T6.

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Driver With an AC Feedback Circuit

In a pulse capacitive driver the feedback is improved by feeding back from a circuit parallel to the output circuit of the driver rather than from the output circuit. This arrangement reduces the interaction between positive and negative transitions in the driver, and eliminates, or at least significantly attenuates, an effective voltage pulse produced in an external load from the driver output circuit during normal down-level operation. As shown in the figure, the driver includes an enhanced alternating current (AC) feedback circuit FC having Darlington pair transistors T1 and T2, an off-drive resistor R1, an off-drive diode D1 and a capacitor T7, formed from a transistor arrangement, connected between the base of transistor T3 and the base of transistor T6. Complementary input signals S and S- are applied to the bases of transistors T3 and T8, respectively, having a diode D2 interposed therebetween. During a normal down-level operation, capacitor T7 is inactive and isolated from any transitions that may be produced at the output terminal. Since the base of T1 is connected to the base of T3, any feedback occurring across the emitter-base junction of transistor T4 is effectively isolated from capacitor T7. With the feedback paths isolated, the sinking of the external load current iEXT into the collector of transistor T5 is now dependent only on the standby base drive and response time of T5. Also, providing the enhanced feedback...