Browse Prior Art Database

Symmetrical, Active-Clamped Driver With Power Supply

IP.com Disclosure Number: IPCOM000034300D
Original Publication Date: 1989-Jan-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Buchholtz, TC: AUTHOR

Abstract

A high speed, active-clamped, off-chip driver function is produced whose rise and fall delays are virtually power supply insensitive. Since the design is for monolithic integration, it is inherently temperature stable due to the tracking of on-chip components. By proper choice of resistor values in a given technology, for known termination conditions, the rise and fall delays through the driver can be made equal. This, coupled with the power supply insensitivity of the design, allows a driver to be implemented with symmetrical rise and fall delays that do not change with temperature or power supply. The figure shows a schematic of the driver.

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Symmetrical, Active-Clamped Driver With Power Supply

A high speed, active-clamped, off-chip driver function is produced whose rise and fall delays are virtually power supply insensitive. Since the design is for monolithic integration, it is inherently temperature stable due to the tracking of on-chip components. By proper choice of resistor values in a given technology, for known termination conditions, the rise and fall delays through the driver can be made equal. This, coupled with the power supply insensitivity of the design, allows a driver to be implemented with symmetrical rise and fall delays that do not change with temperature or power supply. The figure shows a schematic of the driver. The input stage, consisting of devices Q1-Q3 and R1-R3, is a simple differential pair designed for a differential signal with a wide range of input voltages extending from the onset of saturation of transistors Q2 and Q3 to the onset of saturation of transistor Q1.

The design is not overly sensitive to the absolute voltages across the loads R2 and R3 as long as they are large enough to easily swing the differential pair Q6-Q7 in the next stage. The power supply cancelling stage consists of devices Q4-Q7, D1-D2, and R4-R9. The diodes D1 and D2 are optional, but may be useful in efforts to cut power dissipation given the constraints of available on-chip resistance. When the voltage difference (INP-INN) is positive, no voltage is dropped across R9. When (INP-INN) is negative, the voltage across R9 has a power supply dependency, which can be completely eliminated f...