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General-Purpose Driver Circuit

IP.com Disclosure Number: IPCOM000047851D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Scarpero, WJ: AUTHOR [+3]

Abstract

The circuit shown in Fig. 1 makes it possible for the SCS (Schottky current switch) technology to interface with low voltage swing-type drivers. The circuit is comprised of a predriver and a driver. The predriver is an SCS internal circuit wired in a driver cell. When the input A or B is Up, the output of the driver is Up, transistor T8 is conducting, thus clamping the collector of T8 to about 0.2 V above ground. When the input A or B goes Down, transistor T4 turns on, thus resulting in the driver output starting to go Down. Schottky SBD1 acts as a current bleeder limiting the base current into transistor T7. This current bleeder allows control of the Down-going transistor dv/dt to be adjustable. As the output of the driver falls, transistor T7 turns on and transistor T8 turns off.

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General-Purpose Driver Circuit

The circuit shown in Fig. 1 makes it possible for the SCS (Schottky current switch) technology to interface with low voltage swing-type drivers. The circuit is comprised of a predriver and a driver. The predriver is an SCS internal circuit wired in a driver cell. When the input A or B is Up, the output of the driver is Up, transistor T8 is conducting, thus clamping the collector of T8 to about 0.2 V above ground. When the input A or B goes Down, transistor T4 turns on, thus resulting in the driver output starting to go Down. Schottky SBD1 acts as a current bleeder limiting the base current into transistor T7. This current bleeder allows control of the Down-going transistor dv/dt to be adjustable. As the output of the driver falls, transistor T7 turns on and transistor T8 turns off. When transistor T8 stops conducting, the feedback path shuts off due to the conduction of transistor T4. By varying the value of resistor R5 one can control the dv/dt of the driver output Down-going transition. The Schottky SBD3 is required to meet the least positive Up level requirement. Specifically, this diode would appear to clamp the base-emitter junction of T6; however, because of the high forward resistance of SBD3, T6 turns on during the Up-going transition only.

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