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Level Converting Driver Circuit With AC Clamps

IP.com Disclosure Number: IPCOM000041307D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Favata, AF: AUTHOR [+2]

Abstract

The disclosed driver circuit is designed to receive ground-down off-chip levels at input A and convert them to ground-up off-chip levels at output A . Included are transistors TSI and TS2 with their base resistors RS and RS1 such that the tristate function is performed when input Z is Up. For this condition the collector of T2 is Down N.1 V and its base is also Down N.7 V insuring that T4, T7, and T7A are off. The driver circuit is configured with a TTL-type input formed by D1 and T1. Diode D1 causes the base of T1 to have a reference potential N-.75 V which tracks with the -1.5 V power supply. Diodes D2 and D3 with resistor R1 are included to raise the Down-level voltage at the base of T2 to insure AC performance. When input A is down N-1.9 V, T1, D2, and D3 conduct, causing the voltage at the base of T2 to be N.

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Level Converting Driver Circuit With AC Clamps

The disclosed driver circuit is designed to receive ground-down off-chip levels at input A and convert them to ground-up off-chip levels at output A . Included are transistors TSI and TS2 with their base resistors RS and RS1 such that the tristate function is performed when input Z is Up. For this condition the collector of T2 is Down N.1 V and its base is also Down N.7 V insuring that T4, T7, and T7A are off. The driver circuit is configured with a TTL-type input formed by D1 and T1. Diode D1 causes the base of T1 to have a reference potential N-.75 V which tracks with the -1.5 V power supply. Diodes D2 and D3 with resistor R1 are included to raise the Down-level voltage at the base of T2 to insure AC performance. When input A is down N-1.9 V, T1, D2, and D3 conduct, causing the voltage at the base of T2 to be N.5 V, which insures that T2 is off. When T2 is off, T7 and T7A cannot conduct and the voltage at the base of T3 is high, causing the output A to be at the "1" level. The AC clamping network of T5, D4, D5, and D6 with base resistor R4 is included such that any reflections above 2.6 V that hit the driver are absorbed. Transistor T6 with resistors RB and RBB are included to form a DC clamp such that the AC clamp does not dissipate excessive power for the DC case.

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