• Ramping LED Driver  
  The circuit below was designed to drive a LED with an intensity ramping mode.  Two 555 timers generate two different triangle waveforms.  The upper device generates a 10KHz signal while the lower unit produces a 1Hz signal.  The two signals are fed to a voltage comparator.  The result is a pulse width modulation (PWM) signal, which with the aid of the FET, drives the LED in such a way that its average light output slowly ramps from about zero light to maximum and then slowly dims back down.  The circuit should operate over a supply voltage ranging from 3v to 12v. You can easily vary the ramping time by changing the value of the 1M resistor.  For an interesting effect, you can place a 1N4148 diode in parallel with the 1M resistor, with the cathode (banded end) side connected to pin 3. 

• Reduced Power Relay Driver  Aug 3, 2008
  Relays can handle a lot of power.  However, for certain power sensitive designs you would like to reduce the power needed to hold a relay closed.  The circuit below performs such a task.  It uses a single CD4093 quad NAND gate.  When the “on” logic input signal is detected, the relay is first pulsed on for about 500ms.  This is sufficient time to insure the relay is fully closed.  After that initial pulse the relay is then driven with a square wave signal, whose duty cycle can be adjusted.  The signal duty cycle can be adjusted from about 10% to 90%.  In most cases a 50% duty cycle will hold the relay closed.  This reduces the average DC current required by the same factor, which means a 4:1 reduction in power. The circuit can operate over a wide 3v to 15v range.

• SQUARE WAVE DRIVER HAS FLEXIBLE OUTPUTS
  This circuit can produce an output signal ranging from DC to 100KHz. It can source a voltage ranging from 1v to 30v. It can sink a voltage ranging from zero volts to –30v. It can drive up to 200ma of current and can even be switched to a floating tristate output.

One component stepper motor Driver:  (circuit / schematic design added 6/06)

Optical Channel Identification on the ADN284x Laser Drivers:  AN-658 Analog Devices Application Notes  (app note added 6/06) 

Parallel White LED Driver :  National Semiconductor Application Note LM3595 August 2003 (app note added 02/05)

PC's BIOS Interrupt Drives Twin Stepper Motors:  09/14/00 EDN-Design Ideas / (added 6/06) 

PIC LCD and Keypad Driver:  (circuit / schematic design added 6/06)

PIC18xxx8 can Driver with Prioritized Transmit Buffer:  Microchip Application Note Published 9-Sep-02   (app note added 6/06)

Pin Diode Drivers :  National Semiconductor Application Note 02 Mar1999 / (app note added 7/02)

Power MOSFET  Gate Driver Circuits using High Current Super-B Transistors: 6a Pulse Rated SOT23 Transistors for High Frequency MOSFET  Interfacing:  Zetec Semiconductors  Applications Notes A description of the MOSFET converter circuits' requirement for a high current buffer stage, a suggested range of Zetex high current capable, fast switching transistors, and circuit examples.   (app note added 6/06)

Powerlabs Flyback Driver:  (electronic circuit added 1/05)

Power-Supply IC Drives Multiple LEDs :  09/02/04 EDN Design Ideas  /  (added 1/05)  Bright LEDs are becoming prominent sources of light. They often have better efficiency and reliability than do conventional light sources. Although LEDs can operate from an energy source as simple as a battery and a resistor, driving a string of LEDs in constant-current mode can better match the luminance between the devices ....

Processor's PWM output Controls LCD/LED Driver:  05/27/04 EDN Design Ideas  /  (added 1/05)  The PWM (pulse-width-modulation) output available from many microprocessors is based on an internal 8or 16-bit counter and features a programmable duty cycle. It is suitable for adjusting the output of an LCD driver, a negative-voltage LCD driver, or a current-controlled LED driver. cost alternative that provides not only a 4to 20-mA output,

Push-Pull Complementary Power MOSFET  Driver:  Circuit Ideas for Designers Application Notes Advanced Linear Devices, Inc.  (app note added 6/06)

PWM Controller Drives LEDs from High Voltage Lines:  03/04/04 EDN Design Ideas  / (added 6/06)  Powering LEDs from a wide dc range—say, 30 to 380V—without wasting a lot of power in the regulating block, is a difficult task when the LED current needs to be constant. Dedicated LED drivers are available, but they usually implement boost structures and are thus inadequate for high-voltage inputs.

PWM White LED Drivers :  (electronic circuit added 4/05)

Quad MOSFET  Drivers for High:  Supertex Semiconductors (app note added 6/06)

Relay drive protection:  AN319  (app note added 6/06)

RS-232c Line Driver IC Drives Power MOSFETs :  10/24/96 EDN-Design Ideas / (added 3/03)   -Easy to effect an interface between power MOSFETs and TTL circuits