Design Ideas: Circuit schematics, applications, software, videos contributed by electronic engineers from EDN

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Negative-to-negative switch-mode converter offers high current and high efficiency

Budge Ing, Maxim Integrated Products Inc, Sunnyvale, CA; Edited by Martin Rowe and Fran Granville --EDN, 11/12/2009
Don't let variations in input voltage affect the output voltage.

ADC for programmable logic uses one capacitor

Jef Thoné and Robert Puers, Katholieke Universiteit Leuven, Leuven, Belgium' Edited by Martin Rowe and Fran Granville --EDN, 11/12/2009
Use a capacitor's charging and discharging time to sense a user input.

Use two phases to cut current and improve EMI

Goran Perica, Linear Technology, Milpitas, CA; Edited by Martin Rowe and Fran Granville --EDN, 11/12/2009
A two-phase SEPIC has lower output-capacitor current, which also improves reliability.

Fader switch uses inexpensive controller

William Grill, Lenexa, KS; Edited by Martin Rowe and Fran Granville --EDN, 11/12/2009
Control the brightness of an LED or incandescent lamp.

Astable multivibrator gets hysteresis from positive-feedback stage

Robert Larson, Seattle, WA; Edited by Martin Rowe and Fran Granville --EDN, 10/22/2009
Add hysteresis through positive feedback.

Class B amplifier has automatic bias

Pierre Corbeil, Paradox Innovation, Montreal, PQ, Canada; Edited by Martin Rowe and Fran Granville --EDN, 10/22/2009
Biased transistors minimize distortion.

Cable tester uses LEDs to find faults

Pavel Šádek, Apri, Roznov pod Radhoštem, Czech Republic; Edited by Martin Rowe and Fran Granville --EDN, 10/22/2009
Test as many as 16 wires with LEDs as continuity indicators.

Dual-coil relay driver uses only two MOSFETs

Mehmet Efe Ozbek, PhD, Atlim University, Ankara, Turkey; Edited by Martin Rowe and Fran Granville --EDN, 10/22/2009
Detect X-axis position and indicate it with an LED.

Unused port adds a PWM/analog channel to a microcontroller

Vishwas Vaidya, Tata Motors Ltd, Pune, India; Edited by Martin Rowe and Fran Granville --EDN, 10/8/2009
Take advantage of unused pins to generate a PWM signal and then filter it into analog.

Capacitance meter uses PLL for high accuracy

Jim McLucas, Broomfield, CO; Edited by Martin Rowe and Fran Granville --EDN, 10/8/2009
An improvement on an old design lets you measure capacitors from 10 pF to 1 µF.

Resistor compensates for instrumentation-amp gain drift

Kenneth Gustafsson, Karlskoga, Sweden; Edited by Martin Rowe and Fran Granville --EDN, 10/8/2009
Temperature makes instrumentation amp's gain drift; a resistor corrects it.

Missing pulse detects position or produces a delay

Michael C Page, Chelmsford, MA; Edited by Martin Rowe and Fran Granville --EDN, 9/17/2009
A simple logic circuit counts pulses and blocks one of every 36.

Emulate SPI signals with a digital-I/O card

Andy Street, Autoliv Electronics, Lowell, MA; Edited by Martin Rowe and Fran Granville --EDN, 9/17/2009
Four I/O lines let you test microcontroller-based products.

Resistive DAC and op amp form hybrid divider

Marián Štofka, Slovak University of Technology, Bratislava, Slovakia; Edited by Martin Rowe and Fran Granville --EDN, 9/17/2009
A programmable resistance is all you need in a feedback loop.

Connect two buttons with just two wires

Fikret Yilmaz, Mobil Elektronik, Istanbul, Turkey; Edited by Martin Rowe and Fran Granville --EDN, 9/17/2009
Use diodes to steer current in the right direction.

Turn a set/reset latch into an astable/monostable multivibrator

Luca Bruno, ITIS Hensemberger Monza, Lissone, Italy; Edited by Martin Rowe and Fran Granville --EDN, 9/3/2009
Use latches with either active-high or active-low inputs.

555 timer eliminates LED driver’s need for microprocessor control

Michael Day, Texas Instruments, Dallas, TX; Edited by Martin Rowe and Fran Granville --EDN, 9/3/2009
A timer provides programming pulses for lower cost than a microprocessor.

Smart photoresistor timer needs few components

Abel Raynus, Armatron International Inc, Malden, MA; Edited by Martin Rowe and Fran Granville --EDN, 9/3/2009
Smart photoresistor senses darkness and then turns off.

High-performance adder uses instrumentation amplifiers

Moshe Gerstenhaber and Michael O'Sullivan, Analog Devices, Wilmington, MA; Edited by Martin Rowe and Fran Granville --EDN, 9/3/2009
Make an adder circuit using instrumentation amplifiers to increase input impedance.

Nonvolatile standby/on switch remembers its state

Anatoly Andrusevich, Maxim Integrated Products Inc, Moscow; Edited by Martin Rowe and Fran Granville --EDN, 9/3/2009
Remember your circuit's state when the power goes out.

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