LCD Bias Supply Provides Precise Tracking:  05/03/01 EDN-Design Ideas / (added 11/05)

LCD Power Supply Provieds +/-15V LED Power:  Linear Technology Magazine Design Ideas May 2004 (app note added 02/05)

LED Audio VU Meter:  logarithmic scale with3 dB steps, based in LM3915 IC   (added 5/02) Fair Warning: this site has pop-up ads

LED Bar VU Meter:  (circuit / schematic added 2/03)

LED Barograph Drive:  (design added 8/02) Fair Warning: this site has pop-up ads

LED Battery Condition Indicator:  (electronic circuit added 4/05)

LED Boost Switcher: Single AA Cell Powers Two LEDs at Constant Current :  (electronic schematic / circuit added 2/05)

LED Buck PFM: Powers LED with Constant Current Starting at 100MV over VF:  This is a proof of concept circuit which needs improvement. The part values shown will run a high efficiency red LED with a Vf of 1.9V from only 2 nicads, right down to 2 volts. For a white LED you will need more batteries and you must increase the 1.0K resistor to a higher value. Current sensing at a mere 18mV over 1ohm makes this stepdown switcher efficient, but efficiency can be increased by using a larger inductor, improving transistor switching speed, or by increasing the value of the 1.0K resistor. ... (added 2/05)

LED Chaser:  simple10 LED chaser (added 4/02)

LED Counter:  This circuit is the 12-bit binary counter which used 4040B. The number of the pulses of the input can be confirmed by seeing it with the eyes by putting the light-emitting diode to the output of the counter.  It is the function only of it but it is useful. Because it is the 12 bits, the highest rank counter is divided to 1/4096. Because it is, in the highest rank, the signal of 4KHz can be seen in the about 500-millisecond blink. At the input circuit, it is protecting the counter IC from the excessive input voltage with the resistor and the Zener diode.  (app note added 4/05)

LED Decibel Meter :  (electronic circuit added 10/05)

LED Dimmer uses Only Two Lines:  03/21/02 EDN-Design Ideas / (added 05/03) This circuit provides32 steps of brightness control (from0 to100%) for a backlight or instrument panel, using just two general-purpose-microprocessor signals.  Although the circuit shows the circuit driving white LEDs, the load could also be a dc motor or an incandescent lamp. The basis of the circuit is a modified Schmitt-trigger relaxation oscillator controlled by MAX5160 digital potentiometer.

LED Display controller :  ASCII format (circuit design added 11/06)

LED Doubles as Emitter and Detector:  08/16/01 EDN Design Ideas  /  (added 1/05)  Every junction diode exhibits some degree of photosensitivity when it receives light comprising an appropriate range of wavelengths. The spectral response of a junction diode depends on a variety of factors, including material chemistry, junction depth, and packaging. The packaging of most devices aims to inhibit sensitivity to radiant flux to maintain the intended function of the device....

LED Driven Tail/Brake Light Cluster:  LED driven tail/brake Light Cluster Constant current circuitry 12V Battery operation (added 3/05)

LED Driver Application for Portable Products (See also DN23A) #2:  MicroNote 1312 from Microsem  (app note added 6/06)

LED Driver Application for Portable Products (See also DN23A):  MicroNote 1312s from Microsem  (app note added 6/06)

LED Driver Application Notes :  Technique for adjusting the brightness of LED display modules for brightness compatibility. Proper brightness binning of LEDs is critical to the fabrication of an esthetically pleasing LED display. Be it a simple, monochromatic, scrolling message board or a full color video display, the LEDs must share consistent characteristics with respect to brightness to avoid the quilted, patchwork appearance often associated with LED displays. (added 1/06)

LED Driver Combines High Speed Precision:  08/21/03 EDN Design Ideas  /  (added 1/05)  Applications such as turbidity measurement and densitometry require cleanly pulsed light sources with stable amplitudes. The LED driver in Figure 1 illuminates retinal neurons in a biological experiment that has similar requirements. For a given LED at a given current, the intensity is stable, so switching a stable current is a simple and effective way to obtain the needed function....

LED Driver Delivers Constant Luminosity:  06/12/03 EDN Design Ideas  /  (added 1/05)  The circuit in Figure 1 is similar in principle to that of a previous Design Idea (Reference 1) but offers improved, more reproducible performance. The output current is almost constant over an input-voltage range of 1.2 to 1.5V and is insensitive to variations of transistor gain. Transistors Q1 and Q2 form an astable flip-flop....

LED Driver Displays Standing Wave Radio:  03/18/99 EDN-Design Ideas / (added 6/03) The circuit in Figure 1 uses an LM3914 LED driver to directly display standing-wave ratio (SWR) in a low-cost, rugged instrument. The SWR-sensing head is derived from the ARRL Antenna Handbookin an article that describes the tandem match. The forward voltage and reflected voltage (VF+VR ) signal drives Pin 6 (RHI ), and the VF–VR signal drives the normal signal input at Pin 5. You can use this basic arrangement to display the ratio of two voltages in other applications. The internal circuit of the LM3914 comprises 10 voltage comparators that compare....

LED Driver Doubles as Fault Monitor:  08/05/04 EDN Design Ideas  /  (added 1/05)  LEDs find wide use as indicators and as light emitters in devices such as optocouplers. In some applications, the LED or the emitter may be located remotely at some distance from the main unit. Typical examples are dashboard-mounted automotive indicators and industrial optosensors. In critical applications, you may require some means of monitoring the integrity of the LED....

LED Driver Provides Oscillator for Microcontroller:  09/16/04 EDN Design ideas Online (added 1/05) The major building blocks for a white-LED driver are an oscillator, a charge pump, and a regulated current source. You usually use white-LED drivers in tandem with cellular baseband controllers or microcontrollers.