Title:
COMMON MODE EARLY VOLTAGE COMPENSATION SUBCIRCUIT FOR CURRENT DRIVER
Document Type and Number:
WIPO Patent Application WO1995026128
Kind Code:
A3
Abstract:
In a driver circuit for a twisted pair cable, a compensator for preventing appreciable common mode current flow into or out of the twisted pair cable in response to the device receiving a wide range of common mode voltage bias levels. A wide range of external bias voltages may be received as a result of variations in the ground node voltages of two coupled devices. The compensator circuit utilizes a feed back loop and monitors the bias voltage received on the twisted pair cable. As the magnitude of the common mode current increases due to external bias voltage variation from a reference bias voltage, the current flow of p-channel transistors, coupled in an arrangement of the present invention, is increased (or decreased, as necessary) so that reduced common mode current flows onto the twisted pair cable. The present invention reduces appreciable common mode current flow through the twisted pair cable from the driver that are due to variations in the external bias voltage between communication devices. The present invention provides high common mode output impedance for the driver circuit by altering the effective common mode common mode early voltage characteristics of the driver circuit while utilizing shorter channel length transistors for high speed communication capacity. The present invention also offers reduced current supply capacity of the common mode bias voltage source. The present invention operates ideally within driver circuits compatible with the IEEE P1394 communication standard.
Inventors:
VAN BRUNT ROGER W
OPRESCU FLORIN A
OPRESCU FLORIN A
Application Number:
PCT/US1995/003609
Publication Date:
October 26, 1995
Filing Date:
March 21, 1995
Export Citation:
Assignee:
APPLE COMPUTER (US)
International Classes:
H03F3/45; H04L5/20; H04L25/02
Foreign References:
| DE21824C | ||||
| EP0568197A2 | 1993-11-03 | |||
| EP0303407A2 | 1989-02-15 |
Other References:
SUNDSTROM R ET AL: "A LOW POWER DIFFERENTIAL BUS UTILIZING NOVEL SPLIT LEVEL BUS TECHNIQUE", PROCEEDINGS OF THE BIPOLAR CIRCUITS AND TECHNOLOGY MEETING, MINNEAPOLIS, SEPT. 17 - 18, 1990, no. -, 17 September 1990 (1990-09-17) - 18 September 1990 (1990-09-18), JOPKE J, pages 144 - 147, XP000202471
PATENT ABSTRACTS OF JAPAN vol. 9, no. 219 (M - 410)<1942> 6 September 1985 (1985-09-06)
PATENT ABSTRACTS OF JAPAN vol. 9, no. 219 (M - 410)<1942> 6 September 1985 (1985-09-06)
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