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Browse Prior Art Database

High Performance LED Driver

IP.com Disclosure Number: IPCOM000042496D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Balliet, L: AUTHOR [+2]

Abstract

A light-emitting diode (LED) driver circuit is described which provides improved current switching rise and fall times and does not require the use of precision load resistors. It operates from a low voltage (e.g., +5-volt) source and has a high degree of insensitivity to power supply and temperature variations. This circuit uses an N-channel power vertical metal oxide semiconductor field-effect transistor (MOSFET) 1 as the driving transistor for the LED 2 and takes advantage of the unique characteristics of this MOSFET device. This MOSFET 1 exhibits a high gate (G) input impedance, produces a current proportional to its input voltage, is extremely linear, and produces high-current nanosecond switching speeds.

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High Performance LED Driver

A light-emitting diode (LED) driver circuit is described which provides improved current switching rise and fall times and does not require the use of precision load resistors. It operates from a low voltage (e.g., +5-volt) source and has a high degree of insensitivity to power supply and temperature variations. This circuit uses an N-channel power vertical metal oxide semiconductor field-effect transistor (MOSFET) 1 as the driving transistor for the LED 2 and takes advantage of the unique characteristics of this MOSFET device. This MOSFET 1 exhibits a high gate (G) input impedance, produces a current proportional to its input voltage, is extremely linear, and produces high-current nanosecond switching speeds. A high stability constant voltage reference circuit, such as a silicon bandgap circuit, provides a constant reference voltage Vr which provides the precision operating characteristics for the driver circuit. Resistors 4 and 5 establish the LED current levels for both the "on" condition and the "off" or bias condition for the LED 2. For binary signalling purposes, switching of the LED 2 between "on" and "off" conditions is controlled by the binary input signal supplied to the base electrode of a transistor 6 which is connected to the circuit in an open collector fashion. When the binary input level is low, transistor 6 is non- conductive and a high value of gate (G) to source (S) voltage is presented to the MOSFET 1 by the reference voltage Vr . This turns on the MOSFET 1 to cause current flow through the LED 2 to cause...