Browse Prior Art Database

Controlled Output Transition TTL Driver

IP.com Disclosure Number: IPCOM000041557D
Original Publication Date: 1984-Feb-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Gaudenzi, GJ: AUTHOR [+3]

Abstract

The disclosed driver circuit is a push-pull output type designed to convert on-chip logic circuit levels (.2 V to 1.7 V) to TTL (transistor-transistor logic) levels (.6 V to 2.4 V) while limiting the output WV/Wt (rising and falling) to below 1 V/ns. The circuit is powered by a 1.7 V and 3.4 V power supply. The output rising transition is controlled by resistors R2 and RCC and the associated nodal capacitance. As R2 is increased, transistor T3 will turn off slower, resulting in a controlled rise time appearing at the collector of T3 and the base of output transistor T6. Since output transistor T6 functions as an emitter follower, the output rising transition is controlled to <1.0 V/ns. The output falling transition is controlled via active feedback.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 86% of the total text.

Page 1 of 2

Controlled Output Transition TTL Driver

The disclosed driver circuit is a push-pull output type designed to convert on- chip logic circuit levels (.2 V to 1.7 V) to TTL (transistor-transistor logic) levels (.6 V to 2.4 V) while limiting the output WV/Wt (rising and falling) to below 1 V/ns. The circuit is powered by a 1.7 V and 3.4 V power supply. The output rising transition is controlled by resistors R2 and RCC and the associated nodal capacitance. As R2 is increased, transistor T3 will turn off slower, resulting in a controlled rise time appearing at the collector of T3 and the base of output transistor T6. Since output transistor T6 functions as an emitter follower, the output rising transition is controlled to <1.0 V/ns. The output falling transition is controlled via active feedback. The active feedback elements consist of transistor T4, T5, T8 and TFB and resistors RSFB and RT. When input A is at a logical 0 level, transistors T2, T3 and T7 are off and the driver output is at a logical 1 level (>2.4 V). Transistors T4 and T5 are conducting which causes T8 and TFB to also conduct. The magnitude of resistor RSFB will determine the level of saturation for TFB. When input A rises to a logical 1 level, T2 and T3 will turn on which results in T4, T5 and T6 turning off. When T2 turns on, the majority of its emitter current flows into transistors T8 and TFB. As T5 turns off, T8 and TFB will also turn off at a rate determined by the saturated time constant of TFB....