Browse Prior Art Database

High Performance Current Switch Push-Pull Off-Chip Driver

IP.com Disclosure Number: IPCOM000047852D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Barry, RL: AUTHOR

Abstract

A feature of the disclosed driver is that the input voltages are shifted down and the current switch is operated at lower voltages so that the output pull-down transistor can be driven directly from the collector of the current switch instead of being driven through a slow level shifter. Referring to the figure, T4, R4 and T5, R5 are the input and/or reference level shifters which drive the current switch T2, T3. T1, R1 is its current source. If "data" is high compared to "ref" or "data", T2 is on and T3 is off, which pulls down the collector of T2 and allows the collector of T3 to rise. This turns on the output pull-up T7 and turns off the output pull-down T6 which results in a high output level. Conversely, if "data" is low, T7 will be off and T6 on, which results in a low output level.

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High Performance Current Switch Push-Pull Off-Chip Driver

A feature of the disclosed driver is that the input voltages are shifted down and the current switch is operated at lower voltages so that the output pull-down transistor can be driven directly from the collector of the current switch instead of being driven through a slow level shifter. Referring to the figure, T4, R4 and T5, R5 are the input and/or reference level shifters which drive the current switch T2, T3. T1, R1 is its current source. If "data" is high compared to "ref" or "data", T2 is on and T3 is off, which pulls down the collector of T2 and allows the collector of T3 to rise. This turns on the output pull-up T7 and turns off the output pull- down T6 which results in a high output level. Conversely, if "data" is low, T7 will be off and T6 on, which results in a low output level. In normal operation T12 and T13 are off. The load for T3 is clamped in the up level and down level by T10, D10 and T9, D9, respectively. Operating D9 at about 30 percent of T3's current enabled the value of R3 to be increased, which slows the rise time of T7. Building the load of T2 with T8 in series with R2 enabled the value of R2 to be decreased to speed the turn on of T6. T11 is a 1:10 current mirror.

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